Looks a bit dangerous to me, and if you put it in a drill press then you definitely have reached the danger factor! Never ever ever ever do barrel trimming in a drill press. Never ever hold on to a pen blank or part with your hands and use a barrel trimmer either.
Is that top pic a finished piece after being trimmed? If so, it sure looks ugly. Your method as you have it is crude, but no doubt has some success. What you really need is a collet chuck. The center band is really no different than a ring. The best way to make a ring is with a collet chuck. If you stock is square, you simply place it in the lathe between centers and spin it round and even across. Then you put the rod into a collet so it barely sticks out. You now use a drill chuck and drill the rod with the lathe to obtain your inside hole. You then Pull the rod out about 1" and use a live center in your tail stock into the hole to be sure rod is lined up straight as you re-tighten the collet. Now you use a parting tool and clean the face, which also makes the face square with the hole..thus no jig or barrel trimmer is even necessary. I do not use any sanding or barrel trimmers of any kind, just collets, works no matter what size pen you have. After you trim end, you spin the 1" or protruding rod to your desired outer diameter size. You then use parting tool and make a shallow cut according to how long you will want the ring/centerband to be. You wet sand and polish the ring. Then you finish parting the ring off from the rod. The act of parting it away will also square that side of the ring too, so you do not need a trimmer again there also. Now you might have just a tiny bit of a burr on the ring around the inside hole from parting it off. You just grab a deburr tool and stick in hole and give it a couple strokes around the ring to clean the inside burr away. The methods described are the safest way to do things and the most common practice of making a ring with a lathe, and are extremely simple and require no special tools and jigs other than your typical lathe tools and a chuck.
If you wish to do some straight segments into your pens, the exact same methods will never let you down. You can cut rods to length, drill them, assemble and glue them while on a tube and clamp them perfectly square every time.
Barrel trimmers are great if you are making and selling them. You need to replace them as they get old and dull and there's so many kits out there that you need different rods for the trimmers and larger trimmers for some kits, and smaller ones for others, it reaches a point over time that you quickly spend far more than a decent collet chuck in only a years time, so after several years you might have spent enough money on barrel trimmers and trimmer accessories to buy a new lathe too. And the negatives like with slims they always leave a burr on the tubes..you risk over trimming as you can't clearly see what you are doing, and personal injury has come to many a man getting in a hurry with a barrel trimmer..I bet more people have experienced an injury from one of those, even if ever so minor, than have not.
That's my thoughts on it all for what it's worth.
