I would like to try my PU100 on my 335 copy. I have seen that the Roland GK3 has a specific bracket for mounting on a tune-o-matic style bridge and was wondering if would be compatible with the PU100 (width, height, length) if I would get hold of one?

I don't know if the bracket will fit a PU100. But I do know that a Roland GK3 pickup will work just as well as a PU100.