Well another approach, you could use double stick tape to hold it on the sectional door and also use the polyurethane (Sika 15LM or equal). But your door weight will be more and would need additional springs or different springs because you would be adding 150 lbs to the door +/- So, you likely have a door that has 2-150 lb springs, now you would need 2-250-lb springs to accommodate. Whatever you use as an adhesive, you will need a squishy soft set (Low Modulus). The Sika is just one of the market standards, but there are others.
FYI Cypress = 32lbs per cu.ft. of weight converted to bd ft 12 bd-feet = 32 lbs÷2 =16lbs per 1/2" thick cypress. 12 sq ft of 1/2 " = 16/12 1.33 per sq ft x 112 (door sq ft) = about 150 lbs added wood wight + the caulking/glue etc. probably another 10-15 lbs of misc weight. Just keep the weight factor in mind.