Greetings. I have a bike with 20" wheels (Kenda road type tire tread) that I'll be shipping in a box from coast to coast to my brother via UPS. I wish to inflate the tires to help protect the rims, but not so much that they would risk blowing out in the cargo compartment of a jet aircraft at 37,000 feet. Tires are rated at only 40 psi max, so I'm leaning towards 10 or 15 psi at close to sea level, but I really have no idea. Maybe they shouldn't be inflated at all. Your thoughts?