Let me get back to you on that - I have a coworker who asked me to make her a pen to fit her specific favorite refill. I now can't remember if it was a Pentel Energel, or a Pilot V5, or something else. What I do remember is that it was almost identical to a Schmidt 888, and fit into the PSI Rollester I had on hand no problem, with the only caveat being it was about 1-2mm too long. Very easily corrected with a pair of scissors or a hobby knife or what have you.
I'll check tomorrow and if it was an Energel I'll try to remember to report back. If it fits in the PSI Rollester with minimal modification, I would imagine it probably fits in basically any other rollerball kit with the similar minimal modification to the refill.