I use a Shure with my Spacedeck. I no longer use the foam mat and have, instead, opted for a Mat1 from Boston Audio. As a coincidence, the point of thickness where the Mat1 and an average LP combine is within microns of the level where the Shure accepts the stylus if placed directly on the platter. So, I use the Shure on the bare platter and figure I am setting the force as it would be when the stylus ultimately touches the LP, which is what I think Marty is saying. I have increased and decreased the pressure from there and, right or wrong according to Not, this is where a measurement of VTF sounds best to me.
Spacedeck and stylus force guage
I am setting up a Nottingham Spacedeck with Spacearm I recently bought used. The instructions with the Spacedeck say to use scales directly on the mat. The instructions with my Shure SFG-2 stylus force guage say to place it on a record. This will result in a huge differance in pressure. Which is correct?