Honestly your game seems fine to use them like this, as long as the nav mesh itself isn’t distorted, I doubt this would cause any significant performance issue in a game that’s well optimized other wise. It’s just nice to have cleaner collisions and NavMesh hull. I’d go ahead and stress test it as is, and if it works in a series of vents fine, I’d leave it as is.
The permutations would be how many different vent types you have, if there’s 10 you could manually make the collisions but it’s not always worth the effort.
do you just go complex as simple when navmesh fails or fix simple first??
This is dependent on the game, if I’m trying to get the very most out of performance, I’m making as simple a collision first, but a couple more collision points won’t hurt a well optimized or already very small or simple game.