I have seen some folks post that they would be concerned about having a round hatch in the rear. For me it is neither here nor there. If I had one I would be happy but I doubt I will put one in.
I like the rudder controls so I personally don't think they need to be changed. I doubt I would like anything else any more (or less). The one thing some folks have talked about is adding a Boa to adjust the tension. I have not had any issues but this seems like a nice function improvement.
I think the rudder works well and I like not having the twist and stow. It would have been nice if it had recessed fully but that is a pretty major hull change. I hated the block at first, now I am down to a mild dislike, I am sure that soon I won't even think about it.
I think the problem with a lighter hull material is that it would be significantly more expensive and it would be more fragile. I certainly would be happy if my Outback weighed less, but not if that made it more fragile.
I think a front hatch bucket is a nice easy upgrade. I am sure one will be available at some point. Maybe they will make it standard once they do. The other is rear H-rails. I am torn on that one. The bungees provide a lot of flexibility but I would not mind a good grab point at the rear of the kayak. I doubt this will ever be standard, but I hope they will offer it as an accessory soon.
Overall, I am really happy with my 2019 compared to my 2011 (which I still love).
I think the one thing I would like to see is a better front handle. The one on the Outback is a little small. I would be OK with the same style but big enough to grab with two hands. Anyone ever upgrade theirs in some clever way?
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Fish tremble when they hear my name

A ship in harbor is safe -- but that is not what ships are built for.
--John A. Shedd, Salt from My Attic, 1928