Good person to talk to would be Adrian/TODA AU.

I know for B-series VTEC engines he suggests pretty much never increasing the size of valves and has stated that he has used OEM valves in most of his builds. Not sure if this applies to the non-VTEC engines, but anyway it might not be necessary.

The valves I'm using are Jun 0.5mm oversized, which is large enough. 2mm sounds a bit extreme I think man, I'm not sure it would be a good idea.