I am sorry dave, let me clarify something. Are you saying I should still use the full round vent style but only cut one of the two triangles for air inlets? I am making my own vents so I can design it any way, I just want what's best. If I do the full circle vent (but only cut out bottom triangle instead of top and bottom), I think the vent will stay open easier than if I do just the triangle like above. That said, I kind of like the look of just the triangle and I have a way to ensure they will stay open (spring on bolt). Thoughts?