No idea about balancing as I bought it like that, there is a little bit removed which implies it's been done but that could be from before it was lightened.

Yes the counter sink holes will be from Honda. You definitely need to balance it again after the skimming or it WILL crack.

Anyone know what the Tyga HRC copy flywheel plate thing weighs?

No sure, can weigh it for you in the coming week if you need. I recon its about 1/3 of the skimmed unit. I will also weigh my skimmed unit to compare.