Starting on Long mast vs Short mast

[DAnderson]

"Be in deep water and dont rush up to full height
You can foil low down and build up"

I agree with above. Step 1 for foiling = ride the board on the water & gradually learn lift off. Can be similar when changing gear. May be a mast location/foot placement issue if you're strapped.

[rnelias]

I've started on 70cm mast and 1250cm^2 wing and had no issues to adapt to the longer mast (90cm). I think it's crazy how our brain can readapt to different wings and masts very fast once you already learned how to ride a hydrofoil. Probably your board and mast position are not adjusted and you have to work a little bit more to find the point of equilibrium. I had some issues after changing my board and had to reposition the straps but it was just a matter of finding the best adjustment.

[SolarSet]

I had ridded first 40min on must 40cm, then had 4 sessions on 60cm and yesterday first time on 90cm and I can see that 60cm was a waste of time, maybe 2x times I should have ridden 60cm.
In choppy wavy water 90cm is waaaay easier there so much more time to react to foil breaching surface and board touching water.
If I was going to start again I would get 70/75cm must from the start and get 90cm on next foil wing

[SWO_kite]

My guess is that you need to figure out the timing of when you move your weight from the back foot for lift, to the front foot to neutralize. This timing changes with different mast lengths and needs to correspond with how you are moving and powering the kite. You might also not be diving the kite hard enough.

As someone else said, break your launch up into two parts (1) a water start, then (2) bump up onto the foil. Once you dial that in, you can combine the movements.

^^^This

The differences experienced when using different mast lengths is, in a way, similar to using different line lengths with the kite. The length of mast changes the way the foil flies in the water. Pivot point, overall board weight, stability & input response are all effected by mast length. These changes in performance can feel like a HUGE change to someone with less foil riding experience. But experiencing these differences in performance will also help shape your personal preferences for what makes foiling enjoyable to you.

Just keep practicing. Experimenting with larger kite sizes could aid progression.