My two bobs worth ....
I have learnt on a carbon jshapes board with full length mast . I am able to go up and down wind and am just starting to get my head around gybing. I can control height pretty well now - just want to be much better at gybing so I can settle into cruising about .
I opted for this combo based on knowing that I would progress in skill and felt it was gear I could grow into over time . This has been my experience in windsurfing 25 years and kiting 7 years . I am 55 yo .
I have not ridden anything else but am guessing the jshapes is a little more difficult to learn on than the main stream learner gear with short masts etc .
I agree with RAL INN - I didnt see the need for a shortmast - I would have only used it for a short time an felt I would be looking for the longer mast very quickly due to the choppy conditions here . And yes , I have had plenty of crashes from a height

. Helmet and neoprene vest .
The jshapes has a fairly high volume board ... I have found the volume to assist me in light conditions .
There was some wasted sessions at the beginning in onshore conditions ... I got nowhere , too shallow and blown back on shore .
When I had crosshore I advanced pretty quickly - I was going upwind 300m + in about 2-3 hours when conditions were good .
I listened to advice about using a smaller kite than you normally use but found that I was best to choose the kite I normally use to give me something to hang onto . Smaller kites will happen later .
My point is , it is possible to learn fairly quickly - with the right conditions , kite and on a board that is not classed as learner gear .
It's just quality time on the water and it clicks into place .
Cheers