1/8 to 3/16. I think the offset is really pretty forgiving as long as you have the right peg which is a tapered riven octagonal oak peg. 1" is a pretty big peg and will pop a tenon if your not careful. On the flipside, you can probably drawbore a quarter with semi green 3/4" pegs.

I don't like to drawbore dry doug fir, but I'll do about a strong 1/16th. (luckily it doesn't come up often)