Remember if you have a field box that can carry half the shop you will have to carry half the shop to the flightline. I built my own field box that carries the starter battery, about 1/3 gallon of fuel, the starter and a fourway prop wrench. The other half the shop is in a rather large tool box that stays in the pickup. That's where the spare props, wrenches, screwdrivers, knives and anything else I can think of such as glue, a bit of spare packaging tape a piece or two of balsa and all the other things that are usually on the bench when you need them at the field. The 12V battery, the starter and the bit of fuel are the heaviest thing in the field box. If anything else is needed because of a bad landing or other mishap that calls for more eqipment, it's a short walk to the truck and the field box doesn't wear you out on the trip.