Evening crew. Have just picked up a 9'5" Sunova Speeed, which has the GoreTex (or breathable, anyway) vent. Am aware of the function re. air molecules go through but not water).

Having not had a breathable-vent board previously, I'm looking for input on their limits re. if sitting on a beach or on a parked car in QLD summer in the sun. I'm assuming they do have a limit as to how much hot air they can actually let out, but would it be safe to assume for general 'stop for some lunch on the way home from a surf mid-summer' times, is it still a killer to leave a 'breathing' SUP in full summer sun for a couple of hours?

I would never have done that with my Mana as it had a regular non-breathing vent (yes I could've removed it, but I would have forgotten to put it back!).

Advice / experience would be appreciated

Agree with Langers... they are good and don't touch them.

I have had a lot of Sunovas laying in the sun all day at demos, never seen any issues yet.
The standard balsa color never even seems to get hot.... except on the thin part of expose black carbon on the rails.

But I don't leave them out needlessly..... especially if they have dark colors.

I don't leave any board in the sun if I can help it. I have had one custom without a vent blow up like a balloon, after 10 minutes in the scorching central QLD mid summer sun. Not good.
I have only had one issue with the gortex style vents, where it was venting around the threads rather than through the breathable membrane. A quick blow out and it worked fine.
Like all say here, no need to play with them.
I've been researching board bags and white seems like a good colour to reflect heat, some claim even better than silver.