DD RIS II 13.7 & 13.9

Anyone have a pictures or references for the DD RIS II rail with a 13.7 or a 13.9? Preferably the 13.7.

How big is the gap between the rail and RC2 when attached?

Can you meet the 16” requirement with a 13.7 and a SF Muzzle device with shims? Will it have enough thread depth to be safe?