i sell toppers and clamps are the way to go, but there is specific clamps made for certain applications. what type of truck do you have?
i have put a few toppers on where you clamp them on and when you have everything lined up perfect, you drill a hole towards the back on each side and use a bolt for a pilot hole. then when you take it off and are in a hurry to put it back on, you just set the top on, line up and put the bolts through and tighten up the clamps and go.
one other thing is tape, use the kind with the paper backing. stick it on the top and pull the paper off. it is easier to screw the tape up if you slide the top putting it on, but once you clamp it down they don't slide around. ce61