Jim,
If your arbor press is like mine, it has a metal disk in the base that has some notches of different widths. I have seen pictures of a custom fit piece of wood bolted into the gap in the base under this disk, and this would give more room for ram travel. For pressing pen parts, I remove the metal disk, and I use a piece of plywood with a small piece of UHMW plastic on it. So far it gives me the clearance I need. The wood/plastic base are both less than 1/2" thick, otherwise there is not much clearance for a longer blank when pressing fittings.
I also cut a small square of UHMW and taped it with a strong double-faced tape to the ram, to prevent marring of the pen parts.
Finally, for some pens like a cigar, a small wood block with a hole is recommended for supporting the rim of a part during pressing.
One thing I plan to add is a small stand for my arbor press, to lift it so I can see the pressing action better. Also, this would give me better clearance for the arm, which hits my workbench, so I keep it clamped at about its midpoint. I'll try to get a picture of the cigar pen jig I made and post as a follow-up.
Good luck with your press.