Hi toolate. Glad you are getting some waves on it.

I had a feeling your 70kg body weight would handle it OK since the stability for my 80kg weight on this board is my absolute minimum on minimal choppy water. But I haven't used it that often either so I may improve on it if I did.
My next board up is my favourite at 110 litres, Sunova Soul good but not perfect stability in a variety of conditions. If I was 70kg then a board around 100 litres would be the same. And a board at 95 litres would have good but a little less stability too like you & your Supertech.
My most stable board is my JP widebody at 124 litres by 32 wide. Your Stun Gun may feel the same for you. Sooooo comfortable but doesn't perform as well. But great in bad choppy conditions.
So I think your absolute minimum volume board with the Supertech shape would be one at about 80 litres. Which would feel like me & my Supertech. But they really are a lot of work but good for stability training.

So I think you are on a winner.

Cheers & have fun!