With the right gear, you will be able to ride down to 5 knots.
It will probably take some time till you can, as you have to learn first, and then get better and better till finally good.
If talented my estimate would be 2 years at least
Your ultra should take you down to 7 knots, but will be difficult to keep in the air now.
17 isn't the best size for light wind, too heavy and slow IMO.
With a light foil kite you can get lower.
It takes a lot to go lower than 7 knots, so this is the limit you can reach okay no problems, but from there it gets tricky and many swims.