So on mine I put a small hole at the back corner... but on mine I have a wall then the back portion of the van is lined with rhino liner... now if it rains hard moisture gets in a bit but I made it to where I could power wash it with worrying ...No idea either. I park my van on an incline and to to the right rear. That way I just have one corner to perform rust repair in the future. Lemme know if you come up wth something.
I’d rather just go to the Snowbike aisle at Home Depot and buy the drip pan they offer for them for 54.99$. Oh wait, I was daydreaming. Sorry. Yeah I can weld up a fancy pan out of aluminum but I’m too lazy that’s the problem.Just have a drip pan made out of galvanized steel or aluminium, a bit more expensive. We have them made all the time for washing down aircraft engines after maintenance. any side you want. You may want to look into having a drain line -- 50 pounds of snow makes a bunch of water the will slosh around happily when you are on the brakes or gas.