Gents,
 I'm pending approval on an AAC 7.62-SD and starting a 300blk build.  I've purchased a 10.5" barrel, gas block and tube, and a stripped upper at this point.  I'm wanting to determine which length rail is optimal to essentially make for a "no gap" or no "overlap" installation.  I dont want a gap between rail and suppressor, but I also dont want much, or any, overlap to ease removal as this supp. will be used also on my Rem700aac.

Any tips, words of advice, or pics of experience?

Here's a 10.5" barrel and 9" handguard with a 762-SD. It's a 5.56 though. With the same barrel to handguard ratio on a 300, it makes it as flush as you could be, because of the deep socket flash hider.  I'd take a picture of my 300 to show you, but I switched it to an SR-7.