Bongo Fury

I have a JAL converted Bongo with a mushroom roof. The fitted mushroom type air vent has cracked and is leaking, so needs replacing. There's also an issue that the roof sags slightly around the vent, probably under its own weight, which causes rain water to pool in that area and flood in through the vent occasionally.

Question is - do I actually need a roof vent? When we camp, we usually leave a window or two slightly open. And for anyone that knows the mushroom roof design, we always put the 3 wooden boards back in place before sleeping anyway, so the vent isnt open to the main cabin. No one sleeps in the roof.

If the vent isnt needed, can anyone recommend some sort of blanking plate that I can use to cover the hole on the top of the roof. Presumably this needs to be flexible and glued in place with sikaflex or something similar?

Thanks

Not that familiar with the roof you have, but peronsaly id want a vent if i was cooking in the van, or maybe in summer when it gets kinda warm. Totally up to you though depending on how you use her when out and about really.

Any chance of a picture to better understand where the vent is and how big etc?