It isn't a big deal,...
BUT
I may make a difference in the drilling jig you use and having you holes run off center.
I don't clamp my drilling device down nor do I use a back up board for the bottom of the blanks.
I made a sled for my bandsaw using an extra miter gauge and I can cross or rip cut the blanks w/out any drift to speak of.
Wait till you try a curved antler! Now there's real Fun!
I would stick with thte band saw for the cross cut,it will take out the least material and make it easier to line of the grains.
The miter is too aggressive for my taste.
The pen mill will cure all ills.
Remember to test fit the tubes first!
(DAMHIKT)
As far as square goes that isn't necessary,but it must be straight.
I rough out thte corn cobs to get rid of the fuzz berfore I drill them.
I use a home made jig in a machinist vice.