Cut the tang ...
I had a bulgy milled post-ban SLR 96 that had that funky ace extended block on the back.. I put up with that odd setup for about a year an then got the dremel out to cut that useless top tang off...
When you honestly look at the situation, you are dealing with a pretty common milled receiver still imported.. Nothing really special .. not like a milled chicom gun or something that isn't to be seen again..
You are adding all of that extra weight to an already heavier receiver .. All of that extra funkiness and LOP issues.. Neutered usage of an collapsible stock which actually has limited use in this configuration.
When you add all of this extra weight/LOP/funky-weird-looks up, it is silly to put up with that because of a little strip of steel hanging off the back.. Unless you plan on restoring the lower tang and the whole neutered front end back to its natural glory .
Once I cut the tang, added the Ace internal rec. block, pignose adapter w/boss, milspec buffer tube and Griffin Armament M4 collapsible stock, the rifle FINALLY looked/handled/operated like a serious go-to rifle.
Glad I did it... never looked back and was a whole lot happier ...