You can easily convert your Offshore planer boards using your original flags with just a few modifications.

All you need are some suitable springs, and some stainless wire, I used .035", other sizes will also work. And a few stainless washers and a longer stainless screw for the flag pivot.

I have a wire bending jig, this comes in very handy for all sorts of projects.

Form a loop in the rear end of the wire, as far as the bend on the front, you will need to experiment with the length, make 2 90 degree bends going towards the back of the board.

Drill a small hole and use the screw eye for the back release as your rear wire guide, attach your rear clip to it using the split ring in the normal fashion.

I used the existing hole in the flag for the spring, these are pretty old boards with the metal arm, newer flags might be slightly different. I also put a longer stainless screw and a  few stainless washers on each side of the screw so the flag would pivot freely.

I also drilled a few holes in the edge of the board to adjust spring tension.

This is the spring I used.