Steaming in a JennAire

I have a JennAire oven with a vent in the middle of the cooktop; this functions as a downdraft for the cooktop, but also "vents" the oven. Whenever I steam, a noticeable plume is escaping out of this vent. Even though my loaves have shown good results from the steam, I wonder if I should be placing a towel over that vent (I remove the whole steam pan after 12 minutes)? Perhaps I'd get more oven spring and an even thinner crust if the steam were more trapped in the oven. Can anyone else with one of these ranges comment? I certainly don't want to break the oven, but you know, if we can improve our bread by even 0.5% without mishaps, it's worth exploring. Thanks :)