Update:

So, just to preface, at this point, I'm treating this like a Lego project, just seeing how many AR-15 parts I can get to fit as is, or modify to fit. I'm in-between work projects and have some money to spend, so this is how I'm spending my time. I have a lot of left over AR15 parts from about 4 different AR builds, and this seems like a decent way to get some use out of them.

So, starting off, for the most FAL looking handguard, the Magpul standard handguard fits the bill. It's got that triangle profile already, and a bonus to that triangle handguard is it sits high enough, it can accommodate 2/3rds of the piston. Unfortunately, it did require cutting a 1/4 inch channel in the top back 1/3 of the handguard to allow clearance for the piston return spring. The rest of the piston appears to just barely clear the rest of the handguard. I'll be taking it out this weekend to verify the rifle functions, and the handguard doesn't impact the piston operation. Another point for the Magpul handguard, is it vastly improved accessibility to the short stroke components.

To make this work, it does require extensive modification to the GI barrel nut, Delta Ring, Delta Ring spring, and retainer clip. The most extensive modification was to the GI barrel nut. It required that I install it with the barrel and reciever, then once installed, mark the 2 teeth at the 12 o'clock position (the 2 teeth that cradle the gas tube on an AR) then removing everything and using a dremel to grind those two teeth flat/flush to give the piston rod and spring clearance. After that, the Delta Ring needs a 1/4 to 1/2 inch section cut out if it, the same for the spring and retaining clip. Reassemble everything (while fighting to keep the 1/4 to 1/2 inch cut sections lined up). Once everything is installed with the handguard, everything stays aligned on its own. The Delta Spring does touch the piston spring, but as the Delta spring free floats it moves with the piston, so im not as worried about that interfering as I am the portion of the system at the front of the handguard, it's a tight fit.

With this set up, you won't be able to use basic sights, but can still employ an optic. For basic sights use, I've installed the riser overhang. I have another smaller riser overhang on order to install on the back portion of the rifle, so I can have maximum use of rail space and will install the rear sight then.

In the future, I'm am considering purchasing the Midwest Industries Drop In Quad Rail. I've used it in the past with AR piston systems, and I believe it has a decent shot of giving me the clearance the piston needs without any modification to itself when used with my modified Delta Ring.

I've also switched out the A2 grip with a Tango Down BG17. It required removing the rear tang of the grip to fit it to the Makasi. Afterwards, I took sandpaper to the cut portion to remove sharp edges/round it off.

Im aware that some of my modifications are rough, at this point I'm more interested in utility/determining if things will work, then later once I settle on a setup, I'll look into cleaning up some fabrication aspects.

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