Hi KKE,
I mostly use the Leviathan 1150 but sometimes use the 1350. I mostly downwind but also enjoy waves from time to time location depending. I weigh in at around 93 kilos and find the 1150 is brilliant for all but the lightest winds. I don't use wings larger than 5.2m and ride an 80 litre board. In anything above 15 knots of wind I use a 3.5m Flysurfer Mojo wing.
The 1350 is quite the beast and is a pumping machine, it loses scarcely any height when gliding and has a low stall speed you have to experience to fully understand. It's great for straight line downwinding and will turn in graceful carves but it is not an agile wing, don't expect to be cranking tight turns even with a small tail and short fuse. For light winds it only takes one good single pump up and you are away, it extracts every bit of wave energy from even the smallest bumps (you'll notice I don't call them waves) and in the absence of bumps or waves, you can pump effortlessly through flat sections. It's a little technical to master the attributes of these wings when you come from any other foil as it's not like any other wing I've used, but it pays dividends in spades if you need what it offers.
At 70 kilo's I'd say you don't need a 1350, the 1150 has most of the properties of the 1350 but is more agile and a bit quicker. I've had all of my best glides on the 1150. I would still use the 1350 for pumping, dock start and SUP foiling.
I have fairly decent experience with most of the SABFoil wings if you need more info. You can also ask questions on the SABFoil FB groups, lots of European riders using all the wings for freestyle, pump, dock start and DW.
DM