Hey gang so the project has pretty much wrapped up! I received my custom cut shims that I designed myself in Adobe Illustrator. I just had to do carbon fiber, because why not (also got delrin just in case), both at a thickness of 1/8". This also helped create the heel to toe incline that I'm used to. Nice thing is they came out to about $10 bucks each (the delrin was about half that). Due to size restrictions I had to design the carbon fiber shims as one piece (which is why they're joined below), but I just took a Dremel to it. Over-engineered? Probably, but I geek out on this stuff.
I designed the shims to use two of the existing ice blade holder holes to act as stabilizers (two screws below). The goal here was to have the shim really be an extension of the boot, not just something slid between the boot heel and the chassis. BTW I'm using Tnuts and panhead hex screws (6/32 which are on par with what rivets weigh).
Chassis mounted, overhang no longer a problem. Super stable with no rocking side to side.
Old school meets new... H300 now on the 9370s. Took them out for a roll and they're amazing (forgot to get a pic with the wheels on... took them off because I'm getting new RRs that haven't come in yet). Also, while I'm being a mad scientist I'm going to try to run all 688 micro bearings with 608 wheels using Bont bearing adapters. Saves almost 50g per skate... I figure with the heavier chassis I can use less weight elsewhere lol.
Hope this helps anyone else in a similar bind with shims. Any questions let me know!