I am about 75-80kg and am using a 2010 10m airush lithium with a 2007 cabrinha bar/lines.

Around 20-25 knots I build up enough speed to be out of control within about 25 metres (edging moderately & fully depowered). I have to hold the bar all the way out. I can plane/edge really hard and prevent me and the kite from ever gaining enough momentum but it is difficult because sooner or later the momentum will stack up on top of each other and I will be going way to fast.

My question is, how much slower will I be going on a 9m? or an 8m? or a 7m?

My problem is that it is hard to get started. I have to send the kite to 12 to lift me up a bit and then dive it up and then send it again. So I have to pack my speed on top of each other like /send up=2kmh/dive down=4km/ send up 8kmh/ dive down 16kmh/ then stable kite in powerzone and then crash. I can do this in 20-25 knots easy but soon enough I will be in wobble town and face plant into the water. So if I go for a smaller kite, will it make that speed build up at the start harder?

I thought most guys my weight rider a 9m but for me 1 meter bigger and I'm struggling. I also prefer to go slower than faster, but I want my speed to be stable ffs.