Opportunity is missed by most people because it is dressed in overalls and looks like work. - Thomas Edison
Just use steel shims in your frame holders cut from length stock of 1/8 and 1/16 flat steel. You can stack them to create any height you want in whatever head. This was a trick we used when doing HD and stacked HD work. You had to shim the screen, not the machine.
Zoo- after web or other spray tack on top of -roll on wb tack try this...Just use some mineral spirits and scrubby to get spray tack off, let dry and see thatthe wb is still useful. You may have to add a tad in some bare spots, but good to go. We do this and don't have to change paper or any more effort.
Zoo--I wouldn't do it on anything but spot colors with mid-low mesh, for sure. Those S thread screens or high mesh screens might not be too happy about the extra strain.