Hi Ryno15.
I basically did the same as you suggested. At my weight of about 80 kgs I converted one of my rarely used but stable boards. 7ft long but 31.5 wide at 115 Litres. And with foil it made it more stable so I could stay out longer than most SUPs as the water got choppy.
At your height & weight I reckon that the length of your Hypernut would be fine but for me it would be too long as I am shorter & lighter.
Also stability is important. So if the Hypernut stability is good then go & get it converted. But make sure the track or tuttle box is set the right distance from the tail. This distance can be found on the internet. I also viewed where the track box was in relation to the front two fins of a thruster set up. Have a look at the 4 in 1 Hypernut foil board which will give you a good idea of its positioning.
As for the foil. It depends if you want to keep it mounted fully on board & light weight if so go carbon. I don't because it is a bit more cumbersome in lifting & moving & more chance of knocking it against something. Plus storage is better for me. But the drawback is obviously set up, dismantling & rinsing time. Doing it properly will take about 15 minutes before & again after a surf.
When choosing a foil you cannot go wrong with the well known brands. But where there could be a big price difference is in the replacement parts. So check this before making a purchase.
The reason why I picked the Neilpryde foil was due to the great review by Piros. Plus its pricing on the whole set up & parts is good too.
But the draw back with the Neilpryde foil parts like extra wings etc are hard to find in stock at shops unlike most other brands. And for your weight go large or more in wing size. 60 & 65cm mast is a good allrounder for starters.
I have since gone to a smaller more unstable foil specific board at 6ft 8" by 26 wide at 96 litres but find myself going back to my more comfortable converted board if the waters get more choppy. Both boards foil surf great!