andygold

Instead of sealing the coil cover with silicone, you may want to try a product called Seal 'N Peel by DAP.  It's like silicone, and comes in a white with green caulking gun tube.  Thing is, it's totally removable.  Once dry, you can easily peel the stuff off in long strings.  I use it to seal the expandable curtains on the sides of window mount air conditioners.  I seal the tops and bottoms of the corrugated flexible plastic using a caulking gun to keeps bugs out.  It dries in a few hours if you point a fan at it.  Then at the end of the summer, I peel it off and can take the A/C unit out of the window.  It does not stain or pull paint off the walls.  I have not tried to seal a MD coil cover, but I think it would be perfect.  I've purchased it from Lowe's for around $7 a tube, but I've also seen it sell for as much as $12, so shop around.

Who makes the cover itself?  Is it one of Deanos'?