the winner in the face mill war is www.latheinserts.com.
I have some CCGT inserts for my lathe, Korloy but man they are tiny inserts. I can't seem to press the Check Out button on the latheinsert package...
I came across a post by a 30 year experienced machinist last night who said the issue is snapping off the R8 alignment pin in the spindle by using too large a face mill. He seemed to be speaking from experience and went so far as to recommend removing the pin, he said its not a key intended for that kind of torque and if you snap it off its apt to damage your spindle and you may have a hell of a time removing the tool let alone fixing the spindle.
Fwiw - there are more than a couple of people out there swinging a 8" face mill on R8 BPs and clones for surfacing cylinder heads. Not taking heavy cuts for sure but then .006 to .008 is about average to reduce a quench chamber by 1 cc so heavy cuts are not really required.
Yea, I was thinking about this. As I would be using a face mill primarily for truing/squaring material, these would be fairly light (< 10 thou) cuts and I don't see why a 3" wouldn't work just fine for that. If in the case of where all I have is .5" material and need it to be .3" I'll use roughers to get the material close, then true/finish cut with the face mill.
If I wanted a face mill primarily to remove stock, I'd probably stick with a 2". Different strokes, different folks.