I check the oil with the bike upright (not on the stand), with the engine running, on level ground, looking for an 1/8" or so in the bottom of the sight glass.  That level verifies there is enough oil inside to show on the glass, but not enough to interfere with the spinny-around stuff.

I just check it like I did before the conversion.....keep the oil between the marks.  Yes....some additional oil is required, and there is a bit more oil up front.....but the oil pump is in the middle and the gear box is near the back....so I just figured I would keep them in the same amount of oil.

I have not noticed any negative issues.  No additional usage, no additional oil spray coming out the vent hose....no apparent loss of power.