the sg7900 is a nice antenna but it is big and heavy. I broke one mount because the thing is so heavy and I didn't have a spring on it. IMHO i would also keep a nice 5/8 2m whip. unless you are on both 70cm and 2m you won't see a whole lot of difference in using it.
See you on the trail
Couple o' FJ40's, BJ70, PZJ77, UZJ100, TDI