I have only a cheap HT, but I find myself using 70cm a lot more than 2m. Cross-band repeating would be ideal for your 3-4 miles out on the trail situations.
A mag-mount 1/4 wave antenna for 440mhz is about 6" tall and gets me a very clear signal to a repeater 30 miles away, line-of-sight with 5w.
A mag-mount 1/4 wave antenna for 440mhz is about 6" tall and gets me a very clear signal to a repeater 30 miles away, line-of-sight with 5w.