Mechanical modifications are already assumed. No problem in cutting a hole :hammer:
I was mostly thinking in the hardware logic, I know that A3000 are specially nitpicking with A3640 boards. Mine works flawlessly; but I'm worried about the 060 upgrade. I also have your speed hack ready to be assembled in my A3640, I suppose it would be a good thing :-)
About possible overclockings, I can try to reach 60Mhz; it's usually hard to go beyond 30Mhz in the A3000 PCB without fast SIMM rams and other mods, right?