Zack, have you thought about insulation for the convertable top?
Something like duct wrap, can be bought in 4 x 10 foot rolls, in thee early spring and late fall you could roll out over your screen foil side down, then dome your top in place.
Its lite and the new formulations would not have fiberglass dust and are not itchy, would roll up for storage.
1 1/2 inch would give close to R5 where not compressed over the spars
Looks like you can now get 1 inch thick also
http://www.americanhvacparts.com/Merchant2/merchant.mvc?Session_ID=cb2782ac9365b4a9756fb724c5935602&Store_Code=AM&Screen=PROD&Category_Code=duct-insulation&Product_Code=DUWR407M