Most of the slippage problem is from tightening the thumb screw with too much pressure and and that does spread the clamp body and then the problem only increases as it gets to be no longer square hence not as much surface holding the blade in place. That is usually followed by even more muscle applied to try and stop the slippage, which also increases the problem. Sanding the tips does help some as it makes the surface of clamps a little rougher so they are a little less slippery. The solution is really an easy one to fix if one takes the measures to correct it at the very beginning by simply replacing the insert tips on both the set screw and the thumb screws right away. (very small cost to do so). I use about as much pressure on the thumb screw as a 4 year old might use if they were tightening the thumb screw. If one uses their scroll saw quite often then the replacement of the insert tips should be required at about every 6 months. NO ware or speading on the clamps that way and one never needs to reap on the thumb screw using this method.
Now about the Pegas clamps on the Excalibur saws......I recently decided to give the pegas clamps a try and found I really liked them over the stock ones. To my surprise, the reason I liked them more was not because of the lessor vibration, as I really did not notice a difference there. But the part I enjoy most is the design of the the clamps do are not restricted by the tension lever like the original ones have. I found it a big increase in installing new blades. I never have a problem if the upper part of the blade is a little bit too high in the clamps, as they can tend to bend sometimes. No longer a problem using the Pegas clamps. For me it is well worth the little extra price of a clamp for this reason alone.
Dick
heppnerguy