RV Garage Construction - Any Tips?

We converted our 36'x 48' barn to an RV garage, have to back in and be very careful with the mirrors,door opening is 12'w x 14' t. would have made it bigger if possible,have a 50 x 30 amp park style pedestal, hose bibb water faucets on both sides, no sewage connections.when pouring the slab, I put a 24" w x 12" beam under the tire tracks to hold the weight, was told by a concrete contractor that was overkill, 5 years later no cracks.Make it as big as possible
and affordable.Look on Pinterest lots of ideas. Never say never! jg