I want to cut my stock head down to correct the squish and I like the idea of cutting it for O rings at the same time. Problem is that someone has been hacked around my head studs with a power drill to allow clearance for the shoulder on the 10/8mm head studs. The cuts into the head step in by roughly 2mm and leave 4mm of material between the edge of the drill mark and the outside of the edge of the head.
If anyone here has done a cut a head this way before, can you please tell me if this will be a problem, or am I going to need to cut 2mm+ off the gasket surface of the head anyway to allow for the wider squish band.
My bore is at 88.5mm and I am planning on using the Dr Q squish band "15 degree squish angle to .5MM bigger than the bore and set-up w/1.2-1.3MM clearance" as that's all I can find.
Also, I've noticed that the builders who really know 500r's restrict the water passage when deleting the head gasket...is that necessary.

If any specs for my motor are needed...87 motor, 40mm pwk carb, AAEN 500 frame pipe, Oversize YFZ450 radiator, Stock reed cage with Boysen fibre two stage reeds and what looks like a 'proper' porting work though I don't have any idea who did it.

Thanks and I really hope someone can help.

Depending on your skills & understanding I might consider paying a pro to do it.  It's a lot cheaper and faster than screwing it up yourself first then paying someone to do it right.

Having said that, you can also O-ring the cylinder instead of the head. Not sure if one is better or worse than the other.  Also there is a very precise angle you'll need to cut the o-ring groove so that it pinches the O-ring properly and completes the seal.  If not done properly it will leak under load.  Again consult a pro 

On the restricting of the head yes there is a reason.  The restriction backs up the coolant flow and pushes it back wards over the rear of the cylinder to help cool the intake side move evenly due to the tilt of the engine.

I was just at HPR, he just sent stuff to a fella in Australia. Head is small so it can't be too much.  Plus what is it worth to have it done CORRECTLY.