Concerning rig tension, the tension you perceive on the beach in not what you will see when the mast/sail is under load. No matter how tight you try to get it on the beach you will find the lee side stay flops when sailing. All components of the boat (hulls, beams, mast, stays) all flex and soften the lee stay. Your mast is only held up by the forestay and windward stay. When sailing downwind you may see the forestay flopping as the two sidestay are doing all the work.
The Wave racers like to have a VERY loose rig which allows the mast to sag back and to lee for greater speed. This scares me as the mast bangs badly in boat wakes and might jump off the ball in a capsize unless you tie it or leave the pin in.
Bottom line? Beach rig tension
is not very relevant.
Now, how to tension it? Chainplate? 7-hole? 10-hole? NEITHER! Dump the chainplate and pin arrangement. Use a short line and tie a "Portuguese turnbuckle". Cheap, fast, no pins, any length, any tension, strong, and easy to solo. No brainer.
Read my post under the thread called "Suggestions needed for dropping/stepping mast on water".