I was pretty skeptical when they arrived as the wrenches didn't look THAT thin, but a quick test-fit says they're good to go!
Just for redundancy, here are the wrenches I ordered from Amazon after reading Interfan's report:


https://www.amazon.com/dp/B00C11RYKK?tag=vglnk-c102-20
"Stahlwille 10-17X19 Steel Double Open End Spanner, 17mm x 19mm Diameter, 220mm Length, 42mm Width"
Part #: 10-17x19, $22.xx/ea from Amazon at posting time.
A quick measurement on my el-cheapo digital calipers says they're 0.266" or 6.77mm thick at the 19mm jaws, and that's really about all you could reasonably fit on the check nut flats.

No time to actually attempt removal, but wanted to post the thickness and order info for anyone else looking.

Today I gave the wrenches and removal techniques a test run on my 1:7 barrel - which has been patiently awaiting installation of its 51T muzzle device.  The short version is torch the thing until it starts smoking (this took a LOT longer than I thought it should have) and keep torching it until it STOPS smoking (this also took a LOT longer than I expected).  Then you can probably wrench it apart in a barrel vise with two of those Stahlwille wrenches.  I tried the maleante "step on the wrenches" technique but only after torching it the first time (didn't start smoking) so probably not a fair test - or I'm just a lightweight  On this barrel, the flats of the check nut and flash hider were only 10-15 degrees apart, so also probably not an ideal case for the two-wrenches-and-a-fat-guy method either.  YMMV of course, but use the blue wrench LIBERALLY until you get smoke coming off and don't quit until she stops smoking.

ETA:
Over lunch I repeated on the 24" barrel - everything that's been said about that beast so far is true!  I didn't get more smoke coming off with the second torch pass, but after doing so I was finally able to get things to break loose with the two-wrenches-and-a-fat guy stand on the thing technique.  Maybe my luck is bad, but the flats angles on this barrel were the same as the other - providing nowhere near the separation maleante shows:

His looks like about 60 degrees vs my 15!

Regardless I got the wrenches flexing and broke things loose, then was able to wrench apart.  I might have permanently discolored that flash hider by slightly over-torching

I departed from maleante's advise slightly on assembling the muzzle brake though.  I bottomed out the check nut and aligned the brake as he specified, but I skipped using thread locker and in fact found that the muzzle brake didn't seem to move for me when I tightened the check nut.  I'll try running it like this and figured I can always go back and redo with thread locker later.

Huge thanks to maleante for putting this buy and fantastic guide together!  I guess I have to break down and buy the bipod now....

Oh, and this is probably a maleante question too: what's the most correct VFG to attach to the rail? And where?

I don't know that there's a correct vfg, but I know what you mean. The only country I know of that uses this setup up is Uruguay. They use AUG A2's with 24 inch barrel and this bipod setup, in a DMR role.I can't say for sure. But it looks like in 3 of the 4 photos I've seen online, they're using this or something similar: https://usa.caagearup.com/svgg-short-vertical-grip-picatinny . There's a couple pics on the first page. But the clearest pic, it appears the guy is using something else. But his hand is covering it.

All accessories are 15% off at Steyr including this complete kit.