Thanks for the suggestions. Sorry to seem unresponsive, I've been out of town for a week+.
The bigger boats seem to have more places to put things and more accessories, like the net, to attach to without new holes. I also noticed that on some boats the the inner gunnel rail is lower than the outer so things can be mounted on the inner without being exposed when the boat is stored on its rails.
In any case..... Here is what I did
I bought three 2" sections of PVC pipe that nest. Sliced each section in half lengthways. Glued three "halves" together with a hose clamp sandwiched between them to make a PVC piece thick enough to screw into. Mounted a clam cleat on the PVC. Took off the excess and sharp corners. I now have a block of PVC with a cleat which attaches neatly to the rubber hand grip on the Sport with a hose clamp. (a few details omitted for brevity) Relocated the GPS forward on the same grip.
It's not a perfect solution. Among other things it does rise somewhat above the gunnel. It can be rotated below the gunnel but may interfere with the seat strap if lowered this way. It should provide a temporary solution to see how a cleat works out for me in that area and whether it will be OK using the cleat "backwards" or whether I want to try installing turning block. Perhaps it will be a permanent solution, will see.
Now I just need a chance to try it