I've done thios with an early '80 SailCraft mast.

There is nothing different between the pre-bend and soft-rig mast extrusion. The spreaders are different...prebends allow swept-back arms. You will need to replace arms from a soft-rigged setup with those from a pre-bend.

You need something like 30-70mm between the aft edge of the mast track and a straight edge place across the diamonds at the spread arm tips.

You then crank on enough diamond tension to get the luff of the sail to closely follow the mast track. The actual numbers on a Loos guage will vary depending on your spreader arms and even your diamond hound positions (which have changed design & locations over the years).

You may also find the main halyard hook at mast head will fail when you go to put on loads of downhaul in a breeze. The old soft rig was not as highly loaded and the top hook is not strong enough for the new loading.



Mike.