I have not used a kit like that, so take my recommendation with a grain of salt. I recently took a clinic on streamer fishing given by a guide who recommended getting an integrated sink tip line with a 24 foot sinking tip. Your kit has a 12 foot sinking tip. What I would do is not cut the line, put a loop on each end of it and go fishing. If you decide that 12 feet is too long or it sinks too far, then you can cut it into 8 foot and 4 foot lengths (or whatever) and use your remaining two loops, but if it were mine I certainly wouldn't cut it before I'd fished with the full length.