Looks great Etienne,

I've just spent (wasted) the past week making a mesh seat. Aeron chair for a kayak? What a cool idea. Huh. Well....
I finally got it 'right' and went out yesterday. Works good, I made a minicell back..... It did everything it was supposed to but my butt still hurt.

Bottom line? If the seat isn't comfortable, just get a gel pad.

I had one but lost it a couple of years ago. Instead of getting another, I made do until I spent a week .....

The aeron chair idea isn't necessarily a bad one. I worked with a guy who had them in his studio. We'd sit in them all day; worth every cent of the $800.
I found a mesh chair (knock off) at Staples that was almost as comfortable. After a couple of years the webbing material tore.
I replaced it with heavy duty pet window screen. Works great.
I've made mesh dog beds for my dog when she was having incontinence problems. should you try this out, get a $16 canvas stretcher (pliers) from Amazon. No other tool in the shop will do what it does--trust me.
What I figured out looking at Aeron chairs online is that they now come in different mesh materials--which tells me there is nothing special about the material--it just has to be strong enough to take the tension.

The only kayak-use for a mesh seat might be a mesh back, or maybe if you lived in the tropics.