Any cover designed to move the condensation away from the pan is good. Just make sure it's made of an appropriate material. Heck, I was on a maple tour maybe 15 years ago. At one sugarhouse one wall was covered with blue and red ribbons from the state fair. The evaporator was a 4x12 or 4x14' and the hood was made of wooden 1x3's and clear poly was attached to it. It was out about 6" past the edges of the pans and hung about 6" below the top of the pans. From there it was attached to the sides of the cupola.
Whatever works, as long as it's safe and clean.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.