FYI, it's called 'decking'.

You should talk to a machine shop that deals with a lot of Hondas. They should know how much would be safe.

Personally, that seems like a jerry-rig way to raise compression. Once you do that, you can never go back without replacing the head. Why not just get new pistons? That way you still have the ability to change things in the future.

Also realize that when you raise compression, you're putting more stress on the internals and the head gasket. You should upgrade these parts if you plan to raise it as much as you're talking.

JMO.