If you have a TLR with a frame counter, you may be able to reset the counter mid-roll and use the 220 in that. I'm pretty certain I could do that with my Kodak Reflex II (though taking up on a 620 spool and then trying to be certain I get the spool back complicate life a bit); I'd just have to be sure not to wind through after 12, but reset to 1 instead -- that alone would get me 23, and that camera will put 13 on a roll as is (with similar trickery), so another reset at the proper time might get me 26 on a 220 roll. Let's see the lab figure *that* one out.

Of course, I could try it with TXP, and develop that myself -- then I don't have to worry about getting the spool back...