Stud mount with studs lightly dipped in silicon is a good way to go for sheetrock or otherwise. And if you really need to you can also apply VHB/silicon to the letter backs along with the studs, but as mentioned it will tear up the wall upon removal. I've also used high tack vinyl designed for low energy plastics (such as oracal 3105ht) to cut the letter pattern and apply that to the wall first, then VHB tape the letters to that. The 3105 will stick to modern paints that are designed for be easy to clean and nothing sticks except for a high tack. Then you can VHB mount to that and be good to go, the VHB will stick to the vinyl aggressively. I've used this method for about 4 years now and no failures whatsoever. Cut your vinyl pattern with a thin inline to make mounting the letters a little easier. But as many have mentioned some letters/materials are too heavy for just tape application. My motto is "screw and glue" or "stud and glue" in this case. And in my opinion any wall mounted letter within reach will fall victim to vandals/kids/etc, no matter how it's mounted they will find a way. Once in awhile customers will ask me if I have a solution for vandals, and my response is "short of guarding the sign with a baseball bat, there is no solution to a determined vandal"...I made a couple of really nice carved, gold leafed, HDU signs, that I installed into a local park and the vandals were chased away by the police (who my client asked for extra patrols in the area once the signs were up) leaving the sign behind...removed from the posts (carefully I might add) they dropped it and ran. Very little damage to the sign so it was remounted to the posts and guess what, happened again and again. Each time the vandal/thief not making off with the sign but not getting caught either. And I felt terrible that I couldn't offer a solution, other than raise our kids better lol. My biggest confusion in the situation was the motivation of the vandal...they were trying to steal the sign not destroy it. Were they going to try to pull the gold leafing and sell it? It's real gold but not sure what they were thinking, perhaps a personal grudge against the town/park? I can't quite wrap my head around that one!