Here is what I came up with for adjusting the cup depth for different bit stickout.
• Measure the depth of the collet nut, mine are 20mm
• Take the tool or your finger and run down the inner threaded cup
• Place a nut without a bit into the cup
• Measure from top down to edge of the top of the nut, mine was 10.14, just say 10
• Run the inner threaded cup (whatever its called) up so its top is flush to bottom of the recess.
• Place your nut with endmill into cup and measure from top of cup to top edge of the nut
• If it less than what you first measured you endmill is resting on the bottom.
• lets say it is now 2mm, you need to run the cup down 8mm
• Its an 8mm threaded cup so one rotation 360º down is 8 mm
• Measure again until you get the nut resting on the recess instead of the endmill resting.