Springs under turntable

Folks,
Another basic turntable question.... Where do you put the level on the turntable to balance it? Is it at the center of the platter or on the body which hosts the platter? The level position at the center of the platter for my turntable is not the same as it is on the body.

Those who are leveling at the center of the platter, how do you level it after putting a record on the platter? The center of any record is not flat and hence this question. This is more of an issue for those who are balancing a turntable over a set of springs or some float-based isolation tools. 

By the way I have tried a Vibraplane platform, incredibly heavy, to isolate my turntable from the footfall noise but it didn't work to my satisfaction. So far the combination of CSC springs that I designed along with Ingress roller bearings gave me the max isolation from the footfall issue. It doesn't completely eliminate it but reduces it to a great extent, requires a very big hit on the floor/amplitude to move the woofers in the speakers. I think that audiom3 has also experienced something similar.

It appears to me that a complete footfall isolation for my turntable placed on a wooden suspended floor would be very difficult to achieve if not impossible. I am now going to experiment with the next option of wall mounting the turntable and also use some sort of isolation (Spring or HRS Platform) to get to the desired level of seismic isolation.... 
Thanks.

I use the level on the turntable plinth. Left to right, front to back -both sides. If the platter is not level and the table is level, something may be amiss.  
Can you reinforce the floor beneath your room? Lally columns will help.

I would avoid wall mounting in a timber-frame house unless the wall is sitting on the external basement concrete.

Platter and top surface of plinth should both be level, or both should be on the same plane even if not perfectly level. Otherwise, you might have an issue with the tonearm mount not being on the same parallel plane with the platter, which would mess up your alignment for sure. Ideally it should not matter where you put the level on the platter, unless you have a deliberately dished platter, in which case yes put it in the center of the platter.

indranilsen, the devise that has to be level to prevent skating forces is the tonearm. So the best place to put your bubble level is on the tonearm board or plinth right at the base of the tonearm. If the platter is a tiny bit off it won't matter. 
It is absolutely possible to completely eliminate footfall sensitivity. It just requires careful engineering. Any of the suspended Sota's, SME's and Basis turntables will do this. I can take a Sota Sapphire put it on a collapsible card table on a wooden floor, jump up and down in front of it and absolutely nothing will happen other than the suspension bobbing just a little. If you put a MinusK platform under your turntable you will get the same result. Can you make a suspension that will work as well? Absolutely. But, you will have some work to do and you will have to spend some money. I have a design for a suspended platform in my head. The form is easy. It is getting the right spring rates for a given weight and applying damping that are the difficult part. I would use a quartz solid surface material laminated to MDF. This makes a very well damped panel for the base and platform. The spring hangers would be 1" aluminum laser cut to shape, drilled and tapped then anodized. These would be mounted on the base at the corners and the platform hung from them with the springs. On the bottom of the platform I would mount paddles at each corner which extend into cups mounted on the base. These cups would be filled with a viscous oil to provide damping. Soft rubber boots hung from the platform extending over the cups will provide a seal to keep dust out of the oil. There you have it. I should think it could be built for $500 in materials.