Basically there are two different boards for this...
9'6 works for me....it's more about positioning than anything, gotta stay in the curl, so u want a slow board.
rounded rails and a wide tail. I also prefer a single fin...10.5 inch greenough on mine...basically your traditional log style board....nose doesn't even really need to be wide, in fact gets in the way when your locked in on a good nose ride!
Then there are the super wide nose more HP nose riders...like my takky ITP. Also nose rides but in a slightly different way. You can run up the front on a crumbler and it'll let you stay there for abit cause there is a lot of volume.....It's a lot fast er so when you got that good section where my log would lock in ...this can out run it abit. It also tracks at a different angle when on the nose compared to the log...so u kinda go side ways abit.... where the single fin tracks.
Both great boards...just depends on the conditions and how u feel on the day.
get two or three boards...but yeah I reckon 9'6 is a good size, for the avg slightly fat male mal rider....both those are 96