Hi all wondering if you can throw in some suggestions. Past few years I've been doing lots of speed/slalom etc and am going through a gear cut back to get me back to a more sensible set of equipment. One thing I'm considering is getting rid of my big slalom rigs & board and setting up my existing wave sails (4.5, 5.0 & 5.8 and possibly a bigger sail that fits 430 skinny) and then using a large more longboard/SUP board style for messing around in lighter winds. I'd like to be able to SUP it but most keen on being able to sail it in smaller surf. I have a JP FSW 93 which I will probably keep just so I've got something a bit speedy/wavey for bump and jump and getting into wave sailing on windier days. I'm a pretty competent sailor but a novice when it comes to 'proper' ocean swell wave sailing. I can't work it out between Kona / Starboard SUPer / SUP boards - footstraps?, ability to plane etc. Pretty keen on the larger end of the marketplace as I'm 90kg - worried about my car getting airborne with such a big board on the roof - guess its the same as old school 370s though. What works, what doesn't? My main spots for using the board would be port phillip bay, around phillip island (surf and non surf), Inverloch & Sandy Point/Waratah Bay - stay around the corner from woolamai beach in Phillip Island regularly and keen to be able to cruise the channel between san remo and PI and also get out in the waves on a small day at woolamai or round the corner at smaller breaks (both in SUP and sail mode).
Howdy seahorse - I have a 9"8" starboard fish and sailed it with a 5.6 in 10 -17 knts in small waves it doesnt want to plane and they say they aren't designed too.
It was great fun in the waves the added speed from cross off wind was great fun - but I spun it out a few times on bottom turns - technique or why I am not sure - Haven't spun it out in waves without a sail and SUp'd it last night in some nice head high sucky lefts and rights and never felt like it would lose traction
You can putter around flat water and go upwind reasonably easy - haven't put the straps on yet but intend on trying it out soon.
I am not sure if putting a bigger single fin and removing the side fins would help planing.
Good luck - maybe someone else has some experience with sailing sups.
one of the local guys here has a kona 10.5 which he got after using a kona surf. he is lighter than yourself but planes on the 10.5 no probs,
does jump gybes etc. yesterday in stronger winds he was keeping up with some of the wave type boards. it was very bumpy and he was riding like a short board.
he also uses it on light winds for old school freestyle and rail rides etc. not sure what the planing threshold is.
i've used a 9'8 manta sup in no winds and it doesn't seem to need a large fin to get going. for pure sup at 105 kg it's just on the small side. the guy that owns it mainly uses it at neil st reef break and loves it. mind you he did build it. 
I've got a 10'6 fanatic fly sup and am 95kg. I wouldn't say sup's plane in the same manner as a shortboard. Even with a 4.5 on in 10-12 knots the fly takes off even if you just hook onto a big bit of chop. Sups are very efficient hulls but not so much of a planing hull so kinda pointless in using a big sail.
My only reservation for sups as a lightwind waveboard is their construction. If you want a light, easy to handle, good looking board think of them as similarly built as a surfboard so it will be dinged by mast/boom though eva use helps this a bit. You could always go to the heavier constructions though but the light weight is nice when putting them on the roof etc.
If you want something that planes more traditionally and is built to take the extra pressures as a sailboard in surf & can jump then get a kona. If you want something to happily paddle round on in the flat, good fun in sub-planing winds and can take into the surf to ride the waves then get the sup.
Sups are different but they are very versatile and heaps of fun
