The first two pickups I owned had in-cab fuel tanks ('73 Dodge W100 & '77 F150) and I never had any issues with them. I've been running the '77 going on 20 years now. Right behind the seats is probably one of the more protected spaces on the truck, so as long as you run quality lines, you should be fine. I would think that I'd be more likely to bash the lines and wires if I was packing gear back and forth across the tank.