Very cool Wouter...

You said "For now it is a hiking boat only but the design not in principle prevent adding a trapeze"

If you are going to use a windsurfing type wishbone boom you could trap off the boom itself with a modified harness set up...just longer lines than a windsurfer because you wouldn't have your hands on the boom...it would even alow you to tune the rig by shifting your weight for and aft helping the sail to sheet in/out in conjuction with the main sheet line... unlike a trap on a conventional cat that only acts as a counter weight.

Best Regards,
Bob