Interesting on both counts. Im not sure I want to take to my VST just yet, but I have noticed the edge channelling even with a matched pullman tamper.
I havent had "puck suck" but I have had basket suck. It appears to happen when some grinds get stuck between the tamper edge and basket sides while tamping. If I pull the tamper out it will somtimes pull the whole basket out of the pf with it. To overcome that I make a couple of super-light presses with the tamper to make sure no grinds will wedge on the edge, then tamp as normal.
Have you noticed measurable edge channelling differences before and after your VST changes?