Volume can be your friend, it can also be your worst enemy if you don't have a nice channel to paddle out. Thing about longboards is & the dynamics of surface area glide across water is board thickness does not really add anything to glide once you get going on a wave. Reading the line up & placing yourself in the right position is more important & comes with experience of surfing a place you choose to be your local. You just can't beat local knowledge.
I'd recommend a board like 10 x 24 1/4 x 3 if your on fatter waves with a channel. But I would not want to be paddling it out at a shifting peak beachie haha

But does sould like the kinda board your chasing
Not assuming your a fat bloke, you could be 6'5 brick for all I know. But just consider blokes like Jimbo could get by with a lot less volume given the right waves.