As luck would have it the MagMod gel holder I ordered arrived recently; the band holds tight to the flash and the gel holder seems solid on it. The gels seem easily scratched but I doubt that can be helped, worst-case I can bond some gel film to a thin oiece of glass or whatever. It is much easier to change gels with it compared to Canon's somewhat awkward holder. Photos later if anyone is interested.
Good stuff ! I'm highly interested in your experience with the MagMod, it looks awesome.