Isn't it safe to say that the amount of vents depends on what animals you're intending on keeping in the viv.....As they don't all have the same humidity requirements ? More vents for a lower humidity and less for a higher ?
1.1 Normal royal 08 - Percy + Sascha,
1.0 Reduced 08 - Monty,
1.0 Het albino 10 - Gypsy
0.0.1 Bosc monitor - Morris,
1 x 45g Freshie.
...and 1 verrrrry unhappy Wife.......