Quote Originally Posted by Donald Qualls
There are several methods of converting 116 cameras to use 120 film. The simplest is to put spacers at one end of the 120 spools (so you're shooting off center in the original frame mask), to put the 6x4.5 framing track under the red window and the camera's film advance key operating directly on the 120 spool; you can temporarily mask off the original frame with gaffer tape, or use a piece of opaque plastic for a more durable mask, to provide a support for the otherwise free-hanging edge of the film. You'll have to use about 2.5 frames on the 6x4.5 track to cover the 11 cm frame of the 116 camera, and you'll then get 6 images on a roll.

Alternately, if you have a couple 116 spools, you could buy some 70 mm bulk film, cut it to the appropriate length, make up backing paper from two strips of 120 backing (putting the 6x6 framing track under the red window), and use every other number, again getting six frames on a roll the same length as 120. You'd need a 70 mm reel, of course (most older plastic tanks accepted 116, though eBay sellers aren't likely to know it), and the emulsion choices in 70 mm are somewhat limited, but it would let you shoot in the original format (with only a small intrusion of the sprocket holes in the extreme edges of the image).

I've seen web pages that outlined both of these methods; you can easily find them if you google on "116 120 (convert, conversion)" (without the quotes , of course).
We will have unperforated Efke R100 on 70mm bulk rolls in a few weeks.