A few more comments here, at least how I see it:
The Soul is an awesome foil kite for both TT and hydrofoil.
BUT, as you are lightweight, it, and many similar kites, will be too heavy for your winds when 54 kg and 15 m2 IMO.
An average say 80 kg rider who can ride in just close to 7 knots, will correspond to you riding in 5.5 knots same power.
So extremely important with a less tough and UltraLight LEI or foilkite for you, as it will simply not be possible to handle nor hang in this low wind you will be able to ride.
Next thing is, IF you get a 15 m2 foilkite, superlight, it will work just dandy for you and a TT.
But if you later want to hydrofoil, you can not use this 15 m2 very well, it will simply be TOO big and everything goes out of control way to fast (unless you race, but I assume that is not the goal) and turns like a pig in the low winds you will be able to ride, no fun and difficult and extremely limited windrange.
So here you need to go down to a 10 or 12 m2 still UltraLight foil kite, if you want to hydrofoil in the lowest wind but with a reasonable range also.
A 15 m2 for you, corresponds to a 22.2 m2 kite for an 80 kg rider, and only a few racers, not many, use 20 or 21 m2 for racing or practice, not when they go out for fun where they choose a 15 max 18 m2 kite.
Would just mention this, if you have ANY intention of ever going foiling, but dont want to change kite "again" - they are really expensive.
So Chris and others who recommended a 12 m2 UL foil kite might be right, as then if you later want to hydrofoil you can use your kite for this too in super marginal winds.
Also, the power from a 12 when flown faster, is huge, so compensates some for the lack of size.
I think you will barely move the low end, at least not much, on a TT going from a 15 to a 12 m2 high AR UL foilkite, when only 54 kg.
Longer lines makes a big difference too, more power and higher jumps, another aspect that can be used when not racing.
If you are sure you will ride TT now and not aiming for hydrofoil, the 15 m2 UL foilkite is IMO what gets you going the earliest and long jumps possible too
Peter