These look awesome. I have looked at the trim but i was worried about the middle section looking like a open/closed cell arrangement. DO you have to do anything about that?
I’ve used 2 different PVC trim boards. Our local lumber yard sells Azek brand. It’s solid PVC. Embossed wood grain on one side and flat on the other. Our local Menards big box store carries an off brand and it’s identical to the Azek but a lot less expensive. Same embossed on one side flat on the other. Cuts like wood, routes like wood. The seat slats are 22” and I reinforce the center so there is no sag. I’ve had 2 sets go through 2 Michigan winters and they look just like the day I made them. The PVC trim boards hold paint really well. I painted one pink for my granddaughter and it has held up well, no issues. They clean up nicely with Mr. Clean magic eraser.
I don’t know if anyone has mentioned this, but if you are using a clamp vac system and you don’t have a porous waste board such as MDF then the system won’t work.