I've been using the ATS with allen bolts for a couple years. I cut the tip off an allen wrench to get on the two top center bolts easier. An allen socket in 3/8" drive works fine on the others (if you relmove the bolt mounting the water pipes you can swing them out of the way and access several of the bolts easier).
If you get them TIGHT, they stay good. The first time, I torqued them to not over 32 lb and retorqued them several times before they stabilized. The second time, after I had r&r'ed the mfd for other stuff, I ran them in with the air ratchet, and they stayed tight. A couple took just a little tweak a few weeks later, but you get the idea. Of course I put a lot of never seez on them so that makes them slippery too. These bolts are grade 12. 9 which is way over grade 8 and being so short, they don't stretch much at all. The long factory bolts stretch and that helps them stay tright as the parts expand and contract with temperature, and crush the gasket just a bit more, etc.