Review of the SMARTractor and SMARTstylus

You certainly do hear it if the cartridge is off as you not only increase tracking angle error but you also can change skating forces. To hear it you need a system that images well.
For yuks just mount a cartridge way off, say forward and twisted 5 degrees. Listen to this to hear the effect then compare it to the cartridge set up correctly. That effect occurs in degrees. Dynamic range drops and the high end looses it's luster. The image becomes a little blurry. 
The real question is can you hear the difference between a cartridge that is right on and a linear tracker? It would be fun to set up a Schroder LT and make that comparison. 

Dear  @lewm  : ""  MC, If you make an error locating the pivot point while setting P2S distance, it is quite possible to end up with only one null point on the playing surface of a typical LP, or none at all. Plus it could exacerbate tracking angle errors that occur at every other point on the LP surface. ""

You are not only been extremely dramatical but " out of game ", you are wrong and your statement about the null points is totally false.

. Look, say that you need 250mm as P2S distance and you are using Löfgren A so you make the set up and with out knowing your P2S distance is off by 2mm ( + ) ( seems a " normal error " we could have. ). Now:

the null points for 250 are: 66mm and 120.89mm  and guess what: are the same for 252mm and for 300mm too because null points are determined by the most inner/outer groove distance and not because P2S or EL. This is true for Löfgren B or other kind of alignment.

We have to take in count that inner and outer most groove distances are 2 of the 3 inputs to make the alignment calculations, the other is EL.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Dear @cleeds : I think that any kind of option we take trying to make that kind of critical set up at the end always will be non-accurated due to the waves/irregularities in all the LP surface where VTA and VTF are in constant change and we can't avoid those changes.

Now, the other issue is that exist 120g. to 200g LPs and we want to listen MUSIC and not end trying the VTA/VTF on each LP be " accurated ".

If we want to listen MUSIC the best we can do is to set up on an average way/trade-oof and enjoy what we listen to because trying to be anal in that kind of set up makes no sense to me.

R.

@rauliruegas , Your last statement is almost right on. If you have a neutral balance arm VTF will not change over warps like VTA. Best solution is a vacuum table. 

If you mount the cartridge bad enough  you will only have one null point over the playing surface of the record. The other null point may be over the label or off the rim of the record. I think this is what Lewm meant. But, I am not sure if you can get both null points off the record. I'll have to think about that.

The change in VTA between a normal record and a 200 gm record is a fraction of a degree. If you increase the VTA by just an inaudible smidge on a 130 gm record you will cover all eventualities. You are right. It is nothing to get anal about (coming from the mouth of the guy that just bought a SmarTractor). 
One thing about the SmarTractor, it is a pretty thing to examine. Fastidious detail. 

Raul, you wrote in response to my post about the consequences of P2S error, "You are not only been extremely dramatical but ’out of game’, you are wrong and your statement about the null points is totally false."

First, thank you for your constant monitoring of my posts. It is good to know that if you do not criticize one of my posts, I must have been correct. However, I was surprised that your reaction to this last post was so vehement, since I consider you to be among the most orthodox, when it comes to tonearm/cartridge alignment. You have in the past been inclined to advocate absolute accuracy uber alles, and you are positively apoplectic with anger whenever anyone is bold enough to suggest that Stevenson alignment is an acceptable choice, even if one owns a plethora of LPs that have inner grooves that encroach the label.
Second, in this case, when you say that the null points don’t change whether the P2S is set at 252mm or even up to 300mm, are you running your numbers through one of the on-line calculators or your own calculator? Either way, that approach would ameliorate the problem I was trying to highlight. Such calculations would generally include changing headshell offset angle and/or overhang to keep the null points on the surface of the LP. Because my point was based on a situation where you err in P2S, but you don’t know you made the error, and you proceed to select the other mounting parameters on the assumption that you have correctly set P2S at 250mm. I am being intellectually lazy here, because I have not done the math myself, but it does seem you could by making that sort of error, end up with at least one of two null points entirely off the playing surface of an LP (maybe not both null points). Perhaps I did exaggerate or was "extremely dramatical" in saying you might end up losing both null points. I still could be wrong, but never am I "false". I was really responding to that old nihilist, MC, who takes pleasure in pretending he knows all the answers and that none of the answers are important.
So why did I make such a statement without doing the math, besides the fact that I hate trigonometry? I just guessed. The null points are points on the radius of a circle that has its center at the pivot point. As the center of that circle approaches the center of the circle that has its center at the spindle, then those null points get closer together on the surface of the LP, assuming you change NOTHING else. Conversely, as the centers of the two intersecting circles (P2S) get farther apart, the null points would get farther apart. As the null points get farther apart, eventually, at some P2S distance at least one and eventually both null points would "fall off" the playing surface of the LP. Probably no one of us would ever make such a large error in P2S so as to completely lose one or both null points, I grant you that.