Kevin-You have probably figured this out already, but, there is no free lunch. For best performance on a permanent mount you need a fairly long antenna, mounted as high as possible. Since you have a huge reflecting surface of the 80 for counterpoise, you can run a 5/8 wave antenna for best performance.
For trail use, short and flexible is best, hence Eric mentioning the SBB1 which is very short and very flexible. Since it's a 1/4 wave antenna, it's performance is not nearly as good. It works, though, just don't expect super long distance contacts. Compared to CB, it's still miles better.
If you are brave, and don't use a roof rack, you can drill a hole in your roof, and run an NMO mount. This is by far the best arrangement electrically, but, you have to drill a 3/4 hole in your roof! A lip mount on the rear hatch is a good compromise.
I have been playing around this week with some steel whip antennas from Larsen. I am trying to get better performance from my radio and still have an antenna that will take the blows, tree branches, rock overheads etc that are part of every trail. I'm thinking that steel whip may be ideal because it's tough, and easily replaceable if it gets bent or lost. For $12 you can even carry a spare. Just something to consider. I just put the Larsen 150CHW on my 40 and think it might be the ticket for offroading. You could run the 5/8 wave equivalent on your 80. I'm going to try that for Death Valley in March.
