so this is the third time my mag mount has slid off the roof while driving. im using one of those diamond nr770 antennas with the mag mount base and every time i hit about 55mph on the highway it just slides right off. tried different spots on the roof but same thing keeps happening. anyone else have this problem or am i doing something wrong here

Yeah mag mounts can be tricky at highway speeds especially with longer antennas like that. The NR770 has quite a bit of wind load. You might want to try a lip mount or through-hole mount instead - much more secure. I had the same issue with my old setup until I bit the bullet and drilled a hole for a proper NMO mount. Works great now and no more worrying about losing my antenna on I-95

ive been using mag mounts for years and the trick is to clean both the mount and the car roof really well with alcohol first, then find the flattest spot possible. also check if your roof has any kind of coating or texture that might be causing issues. but honestly for highway driving you really should consider a permanent mount - way less stress