I used to use the StewMac thin kerf table saw blade, which was advertised as .023" (.58mm). That worked fine, which is why I started with the .023" endmill. They definitely didn't give similarly wide slots. The wobble of the blade and the tighter tolerances of the endmill combined to make much smaller slots on the CNC.
I've taken .030" passes with a .023" endmill in ebony (remember, this is a ramping op, so that max depth of cut (DOC) is only at the very end of the path), but that's as far as I'm willing to push it. It's really not as bad as it sounds, it comes out to 0.00075" per tooth (normally I shoot for .001"/tooth on bigger bits).
I broke two bits while I was figuring out what speed/feed rates worked best. They're cheap, so I wasn't too upset; besides, education is worth the price