That's a very reasonable concern. The other option is to use the reel set for 120.
"What!?"
You need a roll of fixed-out 120 film for this; in the dark, you'll start the 120 film into the reel, then tape the end of the 127 to it, emulsion out. Feed the combined films in together until you come to the end of the 127, and tape that down to the 120 as well, and finish feeding that film in. I've done this for 16mm film (before I made my ABS pipe tank) and it works well enough, especially for a single roll, and the technique is widely applicable for a one-off processing of oddball sizes -- like 121, if you ever stumble onto some, or the 21 mm film I mentioned a while back that that one Soviet spy camera family used.