Hi Tnott,
Yes, I did use pebble-textured laminate. It was the colour "Sapphire" from the "Dimensions" range from Laminex, their most textured range. The 'Quarry' range from Formica is now discontinued and hard to source as off-cuts, and the Wilsoncraft stuff, such as EbonyStar, is expensive, AND it means getting a full 3mX 1.8m sheet- enough material to start commercial production,

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There is no problem in trying out a smaller separation between the pads too. I made allowance for this by making the separation an orthodox 70 degrees, so reducing is not a problem. First I might look at evening the contact platform, though. This I think is the reason for the pop as I'm not achieving the 15lb per sq inch at the moment.
I hope to get this puppy out to a dark site this coming weekend for the first time. Well, oneday this should happen.