Tough crowd here.
Well, I decided that since I don't have a suitable enlarger capable of taking 6x17 frames, a 6x12 roll film holder was a better bet for me. I have a cheap $189 eBay model on the way. I have a machinist modifying a negative carrier for me to take 6x12. I'll move forward from that experience and see if I'll head down the 6x17 path later.