Gas cylinder dimensions, I don't think this will change. This is straight from Kodiak.
Handguard Front
Gas block front with screw
Gas block front without screw
There is a .015" clearance between the gas block and the inside of the handguard. Any more space and it will cut into the rails or weaken the cylinder walls.
I would strongly advise that customers wait until they have the rifle in their hands before they go buying aftermarket bits... They may find that the stuff that is designed specifically for the rifle fits and functions better than after market stuff meant for a completely different rifle.
Burying the gas system on a piston gun with an AR rail height profile has always proven challenging... just look at ACRs, or HK 416s... most have raised their rails to accommodate piston systems and thus have problems putting handguards over the block while maintaining the rail height. In fact, when H&K were competing for the M4 replacement program with their 416, they petitioned NATO to change the specific rail height for the NATO STANAG 4694 Accessory Rail standards, citing "better accommodation for cheekweld and site picture"... the reality was they wanted to raise the rail to suit the gas system. needless to say, NATO refused and they didn't win the bid with the 416 (for a lot of reasons aside from that).
Most piston gun designs will just opt to not bury the gas block under the handguard as it's simpler to just cover the piston rod.
With all that said; This handguard will fit on an AR15, but I have my doubts about any old AR15 handguard fitting over this gas block.
Note on the image; the dimensions are Metric on the bottom and inch on the top in [ ].
Hope that helps.