|: I found some short mounting bolts with sinking heads and washers that go down 2mm. The washers are 10/16" diameter. Good enough for the soccer skates?
In my experience that should be big enough. If you want to do really good, you can an inset out of 1 mm aluminium, drill mounting holes into that and counter-sink your bolts.
: Whats best to cut the rubber cleats? Saw, xacto or jigsaw carefully?
Now idea on that. Neither would I use soccer boots. But that seems to depend on the continent you are living on. I always used basket ball shoes for my street skates.