Thanks for the replies. I hadn't thought about saving the cartridges and paper (I forgot about the paper). In the old days, I would just crack the cartridge open to get at the film then toss it. I'll have to be more delicate with these.
I'd also forgotten that there aren't any adjustments on the x-15 so I'll have to stick to broad daylight.
If I get any results, I'll try to post them.