Re: U-Haul trailer
My experience with UHaul is that if it is back in the lot without visible damage, then they haven't said anything ... but I haven't drilled holes in a trailer either. You can always get corks or dowls to drive into the holes and pretend you know nothing.
Another option is what I do with my open utility trailer and did with my old pickup. Cut a sheet of plywood to fit, mount the chock(s) to this, and add a 2x4 (or couple of 2x4s to make an L bracket) to reinforce the front and put the eyelets through. This way the board and chocks come out and get stored in the garage when not in use. Be sure to reinforce the bolt heads going through the plywood so they don't pull through; typcially I double up the boards (e.g. mount chock on top of a 2x12 that is securely screwed to the plywood). The front tire sits a little higher, but no worries of pulled out bolts and nothing protruding out the bottom to scratch the floor.
Just an option.