Are you using an older Barnack?
Are you using modern film cassettes only?
Are you hating sprocket holes IN your picture?
Are you not fond of washers under your cassettes?
Don't give up hope! There's a simple fix!
1. unscrew this
2. take off this
3. turn it 180° and screw it back on
Done! Your modern cassette now sits about 1mm higher and you got successfully rid of sprocket holes in your frame
I can't guarantee that the use of Filcas will still be possible after this mod (I don't have any).
Sorry if this is common knowledge, but I've never seen a guide (+ this fix is rarely mentioned) and the sprocket-hole question turns up regulary with people searching for suitable washers.