2: I have re-cut a Tornado classic (overlapping) jib by removing some area from the leech and luff. It is approximately the same as the Taipan4.9, but a bit larger. It was not a good jib afterwards. Removing area from just the luff or leech would be even worse. Re-cutting an overlapping jib to make it selftacking is not a good idea, period.

If you are into homebuilding, building a jib is not a large or difficult project. For a first time homebuildt jib, I would reccomend hand cutting and a cross-cut layout. It can be assembled on a domestic sewing machine. You will do better that way than with any re-cut of your overlapping jib.
If you can measure what luff length, foot and leech length you want on your new jib, I can send you a design for evaluation based on the jibs we have buildt for our Tornado.