I have no problem with your strapping procedure as it looks good but also don't see how his boat is going move fore/aft with the shape of his hull and the rising bunks in both directions and with also what appears to be a stop in front of the keel. The only problem I see would be if a strap broke,Sumner;
I pulled sailboats for a living as a sailboat dealer and was often asked to conduct seminars for truckers and was often asked how to tie down a boat to a trailer. I have too much experience in this field and stand on what I said as an expert.
Sumner
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1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Canada, Florida, Bahamas