Yes, I cut off 10' of the my fly line. What I cut off, I turned it into another tip that I can attach using the loop when I need to do a dry fly presentation. This has to be done so that the line doesn't get too heavy. If the line you are casting get to be too heavy for the rod --your rod might overload and break when making long cast. If you are using an 8 wt slow action, cut 15' instead of 10'. This is so that you don't overload your rod.
If you tell me what your rod weight, make and model as well as the maximum depth you are planning to fish. --I can make the calculation for you. LC13-Leadcore is rated at 13 grains/ft. That is what 13 stands for which consequently is the standard for measuring the sink rate in IPS, Inch Per Second (ie. 13 gr/ft sinks at approx. 13 IPS in still water).
If you have other questions and/or clarification that needs to be done, let me know. I'll do my best to help.