Mine is under the 5th wheel overhang, so rain has never been an issue, but I see how it could be if yours is out, exposed. How about lining the inside of the expanded metal with duct tape? Or duct tape a cut piece of plexiglass (or heck, just a piece of hard plastic cut to fit,) again on the inside. Or if duct tape isn't your thing, you could secure that cut piece of plastic to the inside with RTV.
2015 XLR Hyperlite 30HFS5 (mods being performed regularly)
2009 Salem LA 292fkds (gone)
Nights- ('12)23 ('13)23 ('14)15 ('15)31 ('16)25
2014 Harley Davidson FLHX (XLR cargo)
2014 VW Jetta TDI (diesel sipper, camping support vehicle)
2011 Ram 2500 CC 4X4 CTD, B&W Companion (toy hauler hauler)