crashflow said..I have a Naish 1640 Jet and a 5.4 Wing that I use in flat water and surf with a bias toward surf. I'm still not that good. Can't foil jibe. But I have started to notice the drag on the 1640. Looking for more glide but don't want to get too frustrated while still learning.
Stick w the 1640 until I can foil jibe at least (and save some coin)?
Or move to the high aspect and go Up to the 1800 or Down to the 1400.
I guess the real question is... Is the HA going to be harder to learn to foil jibe than the 1640 Jet? Or am I just confused about the real question.

The 1650 has a nice aggressive lift and is stable to boot for its size it also is reasonably predictable. The issue you may come to if you change too early to HA is they are quite twitchy and need to run much faster in comparison to the 1650. The 1650 and 2000 are amazing to learn jibes, tacks and all things in between as they are soo stable and glide for ages even at slow speeds with ease. HA wings do not like going slow so much and will exaggerate your every move, so foot placement and technique needs to be a little more accurate.
This said, the 1800 is a very nice wing and stable in the sense of HA's. I would also look at your size and intended conditions you ride in. If you're light, then you may wish to hold off, get a little more proficient and go straight to the 1240HA when your skills are there.
Either way you go, you will learn to use your foil. It is all about flight time. Lower aspect foils allow you to get away with things more easily than high aspect ones and they also allow you to ride slower but still loaded for stability. HA's are a blast, super fast and nimble, but they can kick your ass if your get pushy with them

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good luck with the journey, once you learn it, you be amused at how easy it is

Ride safe,
JB