Had a housemate 275lbs., 5’10". His G&S 8’6" x 23 x 3.5 floated him like my 6’ tri did for me, at 155lbs. He sat BB 4" underwater, at best.
Shark took a bite out of his board in '83, making him quit surfing. Port bite, board sat at the surfshop on Balboa and LaPlaya (SanFrancisco) until last year, when the shop went out of business.
He action — what kinda board do you surf now? Those dimensions sound about right to me…keep your tail wide (14.5-15") 12 " up (I find nice + thick helps too).
Re templates…not really that tricky… use a curvy pice of wood on some masonite to draw it up, roughly saw it out, use elec planer to get it ptretty near the surfoarm it perfect! You’ll appreciate the practice and it’ll get your eye in.