My sympathies. There must be few thing that are more frustrating, especially if your in the field and there's no darkroom handy. I use re-useable cassettes such as Jessops sell, which can be unscrewed and re-assembled and masking tape has worked fine here but I have tried to dissasemble factory cassettes(Ilford) and found that every time it was almost impossible to take apart without at least slight damage and was then very dificult to re-assemble so how do you guys manage it?
An alternative which I think I have seen posted involves simply sticking the bulk film to the end of the factory film. That way the cassette is undamaged and the factory spool is intact and is built in such a way that the original piece film will never break free. The other advantage is that factory cassette seem to allow the film to wind on and back more freely. Sounds great but my worry would be this.
1. What tape is both strong enough and thin enough to pull the bulk film into the cassette, given that there is a two film overlap( how much?) and thus double thickness and to ensure that there is no breakage as happened to the OP?