fin specs

aloha can someone help with fin specs i am making a 9’0" longboard 2+1 from the tail where should the box be and also side fins this is a beginner board i also want to make a 8’6" for my friend do you know those fin specs also 2+1. if these work i would like to do a 7’4" funboard do you know that for a truster fin specs. thank you