I am making a couple of Imperials that "suggest" 7/8" blanks. However, the lady that I am making it for - saw a specific Amboyna blank that was a smidgen less than 3/4. I told her I would attempt it. I drilled the hole on the lathe and it worked fine. I want to emphasize that I did not just put the blank in the chuck and start drilling. I double checked for square and triple and quadruple checked that the bit was going in precisely centered.
If you take precautions to be precise, I think an 11/16 blank will work on a pen that recommends 3/4. One thing to watch for is the fact that a thinner blank will be more prone to blow out. The more gnarly it is (burl) the more chances for blow out. Also, some woods are more prone to blow out than others. I have had much less blow outs by drilling on the lathe than with a DP. I still use my DP often but when I want "precision" because the "forgiveness" area is lessened, I go with lathe drilling.
"Forgiveness" is variable, and the variable is the degree of precision that one can achieve from end to end.
