Hi Fireball
I have fitted u-bolts into the toe rail for Tanami’s spinnaker sheeting.
One leg goes through an existing screw hole to save another hole and goes through the timber strip under the gunwale. The second leg is in a new hole.
I have three on each side, two near the stern and one amidships for the guy and tweeker blocks. The sheets through blocks attached to the u-bolts can run to either the sheet or cabin top winches easily.
The u-bolt is a Ronstan RF559 63mmx8mm. You need the length to get through the timber.
Greg