It wasn't that bad actually.
I mean, yeah, it's just a couple of extra steps. I was probably speaking off the cuff too quickly. Also, looking at handguard dimensions by other folks to see what will fit, holy sheit is the WK-180 handguard big. Those who want something different will need to get a handguard with an internal height from top to bottom of 1.721", if I'm not an idiot and measured it wrong (pardon my education, I'm a political scientist, not an engineer). 1.720 is probably fine, given that there's a 0.15" clearance from the block to the top of the handguard according to Mr. Wolverine.
Also you have to take into account the barrel nut design since you have a big goddamn spring in there instead of a teensy gas tube. And because I'm including companies that I've looked at that have pretty light handguards for the length, that means:
Most AR-15 handguards are 1.3" in height. That's a lot of handguards you can't use, which kind of annoys me because I wanted something super light.
Unless I'm an idiot and calculated the internal OD that we need, incorrectly. So which ones will work? According to my research....
Seekins Precision SP3R V3 are a possible option. 1.75" internal vertical OD. Barrel nut looks wonky though, may not fit.
Seekins Precision MCSR 1.8" OD, same big barrel nut issue.
Midwest Industries SP series handguards.
Lancer Systems Carbon Fiber handguards.
Aero Precision Quantum handguards.
JP Enterprises MK III handguards.
Spike's BAR2 handguards.
Yankee Hill Machine MR7 and KR7 handguards.
Clark Custom handguards.
Cool Tubz handguards.
And just now I realized that this crowdsourced spreadsheet might help a lot.
Here's a massive list of handguards with weights, ID and other measurements.