12" arms - VTA advantage?


We have all read the discussions about different distortion levels and tracking error between 9" and 12" arms. I have just spent some time readjusting the VTA on my SME V. As adjustment is not "on-the-fly" or easy like on some other arms, I have decided to set it for the thickness of the majority of the LPs I enjoy listening to most, thinner, classical music, in my case. For the thicker 180g reissues, the VTA ends up being a bit lower in the back than is ideal.

Would a 12" arm not reduce this VTA height difference more that a 9" arm? Leaving aside the disadvantages of the added mass of longer arms for the moment, is this not another advantage of the geometry of a longer arm? Why is this not discussed as much as the distortion/tracking issue.
peterayer
Post removed 
Yes, Viridian. It is clear that the arm doesn't move up or down at the base. But because of the added length, the VTA/SRA should change less with different LP thicknesses. Is this less change great enough to be audible? I guess I should have written that the 9"/12" arm discussions usually address differences in the horizontal plane and not in the vertical plane.

I wonder if anyone has made a study of the SRA differences in percentage terms between different arm lengths like they have done with tracking distortions.
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1297392818&openmine&zzGlai&4&5#Glai
For a 12" arm a 1 degree change in SRA would need a raising/lowering of the arm by about 0.21". For a 9" arm this number is about 0.16"
Sorry, if this is not an answer to your post. I have not tried the mat either, so don't know how it sound. Here's the link and hope it help.

http://www.bluehorizonideas.com/recordmat.html

Cheers,