Reading all of the threads here and it actually seems the best thing to do is not build a pistol with all of the rules and regulations...but this is what I have in mind, tell me if I am off base and could be heading for an orange jumpsuit:

Stripped lower, never a rifle, purchased new from PSA a year ago and been in the safe, will install LPK to finish it off

KAK Shockwave buffer tube and brace

PSA 10.5" upper

The LOP has to be less than 13.5" with KAK fully extended? or Collapsed?

Only way to use a VFG is with OAL of 26.5" with KAK fully extended? or Collapsed?

Thanks,

77

LOP should not exceed 13.5'' fully extended.
The ATF recently tried to measure LOP at a angle, in a court case, from the trigger to the longest part of the brace. Traditionally, LOP is measured in a parallel line with the bore/barrel going from the trigger face to the rear of a shoulder stock. Who knows what they may consider LOP on an arm brace? The ATF seems to be making and interpreting firearm related rules in whatever manner best suits their given case. Measuring at an angle would seem to be the safest method considering the ATFs recent example.
The ATF currently measures braces fully extended. Just remember, fully extended should not exceed 13.5'' LOP.

if you use the KAK SB15 tube (8 1/2") and a rubber end cap only, you will be at about 12" even if measured diagonally from the trigger...I went to this set up because of all the vacillations from BATFE... works nose to charging handle if you square to target

Big +1 I'd seriously consider the SBA3

With all the confusion lately, I just dont run a vfg on my pistols.

I have your same setup with the PSA 10.5" A2 upper with Colt handguards.  LOP is 11", and OAL is 28" with a Troy Claymore linear comp.  I added a short piece of rail on top for an Inforce 400 light on an offset angled mount.  It's my home defence and travelling companion.  Shoots great!!  Just recently replaced the mil-spec trigger with a LaRue.  Haven't had a chance to test it out yet.