how to get the SME 309 tail down-help


Have mounted a shelter 501 on my just- acquired SME 309.The word is set the arm tail down for this cartridge but I can't find a way to do that. I start with the tonearm level while the stylus is on the record-as per the SME instructions- using their template At this point the rear bottom  of the tonearm -, which is tapered downwards towards the rear- is about 5mm from the record surface ,which is where SME recommends it to be. If I try to lower the arm from this point I have only 1-2 mm max  before I am in danger of the arm touching the record as it traverses it during play. If I had a warped record  or thicker record it would likely touch it. I tried putting a mat under the record to raise the catridge end but of course this lowers the pivot end of the arm to a position too close to the record surface, as above.Help please??

rrm
It sounds like your playing with VTA and that should not be set by the arm manufactures guide lines you should set it to the specific cart your using ( spacer if needed) the height of the back of the arm raising or lowering will affect the stylus angle in the grove you want this to be approx. 3 degrees so set the height based on the stylus angle, this can be also set by listening I'd google VTA set up and adjust the rear height as needed. 

Also keep in mind adding a spacer will add weight to the effective mass and will also effect resonance frequency of the arm cart system, in your case this could be helpful. 

Looking at https://www.vinylengine.com/cartridge_resonance_evaluator_results.php?m=Shelter+501&cm=8.1&d...

I'm thinking your really close to being in the bad resonance frequency range putting that cart on the SME 309, google shows 9.5 grams effective mass that's not in the happy range for resonance. 

I hope I've made a mistake here on my search for numbers and your ok but please double check.

Glen 
Thanks to all for the suggestions.I will look into a spacer. Glen: you are right about the resonant frequency calculation showing it to be too high for this combo. Nonetheless the 309 is recommended as especially suitable for low compliance cartridges such as the Shelter.I will try adding some weight to the headshell.That should bring the number down even though it won't solve my tonearm down issue.