Shortboard dimensions question - help

I rode a “big guy shortboard” when I traded in the lineup the other day. i really like the thing, but got no dimensions (it was about 7’ x 21" x 2.75). It was still a little too big. I’d like some advice on dimensions (length, width, nose, tail, and thickness) that a 175 LBS, 5’9" guy could ride. I’ve been surfing for about 2 years on that 7’8" bruce Jones posted in the classifieds and I want to jump down to something closer to a real short board. That thing is too big for more radical moves. Something between 6’10" and 7’ I’m thinking. Any recommendations or things to consider would be very helpful thanks