My super ikonta iv does not allow the user to ability to advance using the window. Each advance/spool on is predetermined and locks in place with counter. The window in the back is to check if there is film in camera only, and not to place frames.
It's been documented online quite a bit that this camera needs about a 2inch section of backing paper taped to leader to have consistent spacing. I do it and it works fine, but can be a hassle if you shoot more than one medium format camera in the bag. You also have to plan ahead with the tape and rubber band/ use 120 canisters.
This got me thinking (yes, dangerous!) -- how much unexposed film is left at the end of your frames? Depending on the loading procedure, maybe you could advance past the "Start" line an inch or so more than normal when loading to get a little more buildup on the take-up spool. My Ercona II uses the red window, so I've not personally experienced this problem, but I'd say there is almost two inches of blank film at the end of my rolls (Acros & 400TX).
Strangely, with my Ensign Commando it is the other way around, if you use the internal frame counter then you only get 11 exposures, but if switch the counter off, (it has a simple switch which either sets the counter, or allows use of the red window) then you get the full set, with my Super baldax I get twelve whatever I do,
Originally Posted by Peltigera
With your Ikoflex is it a dual size,? many cameras were either 8 6X9 or with a mask 12 6x6, I have an Ensign 820, which is as the above, I generally use it with the built in mask aas 6x6
My Ikoflex uses the 6x9 numbers for 6x6 pictures - it dates from before 6x6 numbers were universal on 120 film. Hence, use the window for frame one and then the internal counter.