The instructions that come with the R.E.A.L silicone gaskets say to initially torque to 25 in.lb., run the engine, then re-torque to 20 in.lb. Originally, I had the same concern as you about the screws coming loose, so I tried some blue Loctite. I wouldn't do it again, though, because it prevents re-checking the torque during the annual condition inspection. Just be sure to use the Lycoming pan-head screws with the star lockwasher and you'll be OK. The one thing you don't want to do is over-torque those screws, That pinches the gasket and guarantees a leak. (Ask me how I know)
Also, before installing the rocker covers, be sure the surfaces are flat. Mine weren't, so I placed them face down on a heavy wooden bench and beat the flanges flat with a hammer and a piece of wood.