I tried my 78ltre with the 4.8m ( Sailworks Hucker so equiavalent to c 5 - 5.2m sail powerwise ( Bruce peterson said..). Worked well but I was pretty overpowered so it scared the b out of me!
..Think the biggest challenge is going to get the sailor confident 
..After the stacks last year I'm still not back to my earlier blase attitude to the board bouncing around everywhere..
The Pocket seems faster than my 95 ltre when its up & going..Getting used to highwind boards is scary as you have to go out in big wind + chop..
I think (really hoping this is the case
) I've been through that phase. Trick is to avoid those little crests just starting to break (or just broken whitewater) and catching the rail. They seemed to be the cause of most of my unexpected stacks.
So now I just go round those bits and keep the power on and the legs flexible to bounce over the rest of it. Actually makes it fun steering in and out and keeps the speed down too I guess.
Intrested in the fact you want to power or over power a board to get it planning ..... is this the only form of sailing ?, obviously everyone has to put sail power through the board to get planning ,and i agree once your planning and lit on a smaller board when it windy so be it .....but you have to get moving /planning first ,make ground ETC ETC ETC
Fink my point is when your under powered and the board just wont plan and sinks to your waste Volume / surface area is critical. small sail or big sail will not make a significant difference.
Get the volume width and surface area right for your weight and you can have any size rig on that board and still get around .
