Just thought I would share what is working for me..... I have two Robo C2's, running Build-Tak stickers on the build plate. They do not currently sell 5.5 x 5.5 stickers, so I purchased the 6.5 x 6.5, and cut an inch off both sides. Here is how I set the Z-Offset. I bring the nozzle up to where it just grabs a yellow sticky note. Tight enough that I obviously feel it when I slide it back and forth, but not too tight that the sticky won't move. Then I hit the Z minus three times. This gives me great adhesion during the build, yet It will come off with the slight flexing of the build plate.