If you think crosscut was fun you should try anglecut.Nice lookin pen,I like the zebra.
Cross-cut in 99% of woods is the most fragile and difficult cut to work with, as it at 90° from the grain direction (for burls works differently...!), any of the most common diagonal cuts, either 45° or 60° from the grain direction, represents a proportional difficulty and fragility degree, what I mean is, if straight cut or cut with the grain as commonly known, is the 0° or beginning of angle cut rotation, the higher the angle the higher the degree of difficulty and fragility of the workability in the vast majority of wood/timber species.
The biggest risk of destruction of the cross cut pen blank, is precisely while the blank is still in one piece, where dropping it or bending it will snap it in half, reasonably easy (some more than others, off-course) therefore, as soon as the blank is cut in 2 pieces, the risk is reduced greatly and the drilling if assisted as a precaution with some good wrapping tape, it will drill effectively without any dramas, the destruction risk is then totally resolved with the proper gluing of the brass tube(s).
The second stage or, blank destruction possibility is when the blank is attempted to be turned from square to round, particularly at too slow speeds (faster the better, here) with aggressive tool contact and non-sharp cutting tools. If the wood survive the square to round turning, getting it to the final size and shape is without some great risks, particularly if the tube wasn't glued properly to the wood.
Extra care is required to handle cross or diagonal cut blanks/woods, no doubt but, for those that are willing to use whatever works best, safer and quickest to get the job done "SUCCESSFULLY" I strongly suggest that you try the
"Flap disc system" and make your own judgment of its effectiveness on these fragile or difficult to turn blanks/woods...!
Now, in regards to Twissy Zebrano pen, feel your pain mate but, if you have finished it is because you were determined to get to the end of the job and have a usable pen, that seems you have achieved so, congrats, it looks pretty good...!
Cheers
George