There aren't many places on RC airplanes that locktite is needed. If the screw is going into a hole that is tight, such as into wood, there is plenty to hold it there unless something is wrong. The only place I use it is on the engine mount, both the mount to the firewall and the engine to the mount. I use very little, and mostly to seal the threads from oil getting in. The problem with locktiting a screw in is that it can wear loose without turning, but when you check it it still feels tight. Imagine that scenario on head bolts! You'll go nuts trying to find the demon in your engine.

BTW, the biggest reason for head bolts on these engines going loose is because of the large amount of expansion that aluminum has with heat. The hotter the head gets, the tighter the fastener gets. If it's too tight cold, then you get deformation in the aluminum when hot which results in a loose screw down the road. If it's perfect hot, then it's too loose cold and can vibrate looser. Torque specs are much more crucial for aluminum engines than iron because of that property. A proper head bolt stretches with that expansion, holding well enough to seal but not so well to make the aluminum deform. A lot of that break-in loosening has to do with finding the right middle ground torque wise, and letting the bolts take that small amount of permanent stretch that they will when new so they settle in and return to the same size cycle after cycle.