I'm with George on this one. If I'm making calls I'll rough turn both parts and drill the barrel undersized, in order to re-drill it after stabilization.
I used to stabilize regular square cut blanks, then I started roughing them out to a closer size to final and learned that I could get a lot more of them in the vacuum chamber, it took a shorter amount of time to complete the vacuuming process, and it used less "juice" due to smaller mass of the blanks.
I do the same thing with pen blanks, round them out and drill them with a 7mm. Then when you want to use them you re-drill them (even 7mm works), glue the tubes and go.
Happy turning - Tom