Lengthening the boards will not help. Its the overall shape that limits the performance. My 18 is also set up like yours and when running against F18s the lift created by their daggers is quite noticeable. My thoughts were to sleeve the existing wells to allow some newer design. My current path is to locate some damaged Tiger boards to create the sleeve. Another option is to buy the dagger well for a tiger and build from the well. Getting the board in the right spot is the most difficult part. The TheMightyHobie18 boards kind of slant back, not straight up and down like newer designs. Finding the proper alignment both left to right and front to rear will not be an easy task and will most likely require some professional guidance. I will be interested in any ideas or attempts to do this! I have some hulls now that are trash and think I may have access to some damaged boards to start to work with.