I just wanted to address doubts on this bottomless pf -
I have been demonstrating the unit on a SIlvia in my shop for a month and after dialing it in I have zero problems with drip over sides or tightness of PF. I have used triple baskets (coarser grind) and several double baskets to excellent results.
The key is proper dosing. After tamping you should be able to insert the pf without pressing the coffee into the group when the handle is engaged to the red dot on Silvias group cover. After the extraction the coffee will have expanded and you should see the impression of the screw in your puck.