Last session I used 5m lines on it for half an hour. But the wind was not really strong enough to make waterstart enjoyable. The 4 starts I had to do during that 30 minutes / 10km were a bit of a pain.
So I switched to 7m lines that I have been using for two sessions before on the 5m and 7m Hyperlink and that worked fine again, no issues to get started.
For the record, my board is 120x42cm and I have been on the Moses race wings 2018 (and later also one of the new Moses SUP/surf wings, interesting to kite on too), and I am around 85kg.
I do not think this is super important though.
You asked about 25m lines, well... it depends on water conditions mostly if pushing low-end. Perfectly calm water compared to messy moving water makes a massive difference.
I have not pushed low end riding like this with the 5m HL as I have been doing with the 6m R1 before, or before that on the 5m Reo for example.
So it would be guessing. And then it is also a question of what counts to be the low-end. If pushing it in the right conditions I am sure I could ride back and forth in under 10 knots.
Not sure if this tells you much really...
Cheers,
Frank
www.famousfrank.com