Why not do something like this? we have had this attached to the end of a table for 10 years. The roll shown is 24" on the bar, just slide on whatever size you want, no worries about moving a clamp back and forth. Super quick and sturdy. That is a fence post by the way.
No these are really good. They have indentations that are equally the same on both bars so they are always at the same height.Looks like a clever gadget you could throw together from a couple of bar clamps and some odds and ends. One problem though, how do you make sure that both of the spools are level with each other. Not so easy with bar clamps. Just a wee bit mis-aligned and the application tape roll is not parallel to the table top and you get wrinkles, More better, a Weber style device.