Hi Frederik,
Good to hear you are progressing nicely there. Are you using the Duotone Academy App for learning tacks/other moves - well worth a look. For your weight and skill level, I would recommend to go to the Free range in 1750, as a first step down from your 2400 - our best allrounder and easiest to learn tacks and gybes etc. Glide will have more pump/longer gliding, but harder to get going. Carve best for Wave/Freestyle use, also slower to start and I think the 1430 is still too small for your weight and level. You'll be best off with the Free, a great allrounder!