here is what I can muster, with 2 fingers. Yes only 2 fingers worth of downforce, and I'm sitting on my ass, while doing it

yes

only a small round dab, smack in the middle.... I am crazy indeed .....

so what you guys are saying, is that once I get to a perfect footprint, evenly over the entire core, with no room left between the core and the sink, having more pressure on it, will improve things, I can honnestly not see how......
I mean I used 2 fingers to get the perfect seat, and I was not even going at it all the way.... I'd guess about 7 to 9 PSI on the actual core, max....(considering the core is much smaller the 1 square inch. my fingers are puny little stumps, maybe capable of about 3 LB of pressure... (I'm a wimp! I know)