Quote Originally Posted by Wkdintent View Post
Do you mean I let the HDPE base scrape on the floor, or that I could just attach something (like a dome nut) to the underside without a bolt?

If you mean the latter, I would probably stick with a bolt, as it's one of many attaching the base to the chassis anyway.
even if you don't counter sink the holes you don't need to use a bolt to act a caster, HDPE is slippy enough plus if you look at all other modern flippers they just run with the wedge planing the the floor. as look if you plenty of ground clearance everywhere else you should be able to drive around fine.