Well this is cool. You're both PCS customers.
Steve,
I can't answer you. Getting a negative pressure would depend on how tight your chamber turns out to be. How much air you want to move would depend on what you are drying. I have seen big, power vents run constantly with soft maple and I have seen small vents run intermittently with oak.
We don't stock much for conventional kilns. We are pretty much limited to vacuum kilns except for control systems. McMaster-Carr is as good of source as any. They have a lot of vents with louvers. Some are corrosion resistant.
Thanks guys.
Den