I have just got a second hand Jp SLW pro 2015. Only had it out once in about 5 to 15kts with a reflex 9.7. It does everything i thought it would and i love it. Sails just like a free race slalom board. I am over 100kg and got it planing before the light weights. On my othe gear like 7.8 and 80cm wide boards i am the last to plane. Handling the big 9.7 is no drama on this board pre planing. Lots of deck area, buoyancy and stability. I assume WA and light winds means washington? If you want to get going in light wind, seriously consider a full race sail, big with lots of cams. They are a bit big and need a bit of muscle to get going, but it is easier to get planing with them and once going i dont notice any real difference in feel, except that you ate planing insread of wallowing. The jp56 fin that was in mine seems fine.
if the wind is too light to plane, it chugs along quite fast. First time ever i chugged past other grovellers

On smaller gear i am usually the slowest or
sinking
footstraps outboard and second hole from back suit me. Cant see any reason for the inboard strap positions, if you are out of the straps there is either no wind or you are gybing. Dont worry about the big sail, the board is so stable compared to say a 70cm 110freeride its like standing on a ship compared to a log.
i havent been on a us, or the 2016 jp slw.
it easily sails cross wind, upwind and the bear aways downwind, even in light winds are a good rush. I havent had it in any significsnt chop so cant comment on that. Bite the bullet, its a great concept and i love it.