My 14yo daughter wants to start using harness. She can plane on 125l board, is about 155cm tall. Whats a good harness line starting length? Adjustable?
Thanks crew.

26 inch- they learn quicker and trust the harness much sooner if their back foot is bolted down. A board that has a centre,more forward training strap stops them from getting catapulted and from being afraid of the harness.If need be add some footstrap plugs to a board.
PS I hope your not planning to use that SPEED 125 for her to learn to use footstaps.

KA360, No,No, not the SS125L! Thats a once in a while ride.
Similar vintage though. Bic Presto. Haha. She loves the psychedelic Austen Powers style graphics. Sails it well. Beachstarts,uphaul, tacks,gets it planing. Using 4.4m youth rig. So harness time n Let her Rip! Id think..

A Bic Presto is not too different to the SPEED. The mast track is to far forward for her to ever be able to get in the footstraps with a kids rig.
But you can make it workable by fitting another mast track further back behind the original one . While you have got the epoxy out put in some more footstrap plugs forward of the rear straps. With those modifications she will be planing in the harness and footstraps before Christmas and then have all the school holiday to master jumping and gybing