I personally would rather the compressor run less amount of times for a slightly longer period compared to frequently starting and stopping. Most people in club I was in, before I moved, ran bigger tanks they could be at a show playing with thier switches and not fill up, compared to some members with smaller 5 gallon tanks would hit thier switches a couple of times and wait for their compressor to catch up. Your compressor will run the same amount of time with a 12 gallon has a 5 gallon, because you are using up the same amount of air, with a bigger tank it will just take longer to fill but not has frequent. I was only suggesting to run the biggest tank you can fit, if you can only fit a 5 gallon then thats all I would have but if you have the room, maybe between the frame rails or something, then I would get has big as you can. He doesn't seem to be such a big deal since I think virtually all compressors worth looking at are 100% duty cycle.
Just my take on things.
Do you have any pics of you ride offroad87?