I'm awaiting a reply from you on my post but I'll chime in here as well. I'm currently looking into a couple of manufacturers...Florian and BC. Both are being very helpful and their structures look impressive. Obviously the PC is cheaper than the glass by a bunch. However, the clarity of the PC from both is just horrible...if this is important at all to you. We want to save on cost everywhere we can and my wife is strong on sticking to the budget, but even she couldn't stand the looks of the PC and is now probably willing to bust the budget some to avoid it. This really is odd though. There are companies out there who are making PC with clarity nearing that of glass and the price per sq ft is nearly the same. I can't understand why these big manufacturers would not offer this...unless they are really pushing their glass.

From the info I'm getting back from these guys, your temps will be much easier and cheaper to attain than the winter temps I'll need to keep. The double pane insulated glass has a better R value than twinwall PC. The sample I received is very thin indeed...embarrassingly thin. I really can't see it being much help at all in the winter. Florian offers several grades of their glass and has a do it yourself pricing program. Figure on up to a 30% discount on the totals you recieve...else your heart just couldn't handle the strain! Light levels should be fine for either one. These things are much more expensive than I really imagined. Here are some R values that BC sent me:
4 ½ mm twinwall is 1.5
our 6mm twinwall is 1.59
8mm twinwall is 1.65
our 16mm triplewall 2.5
3mm single glass is .90
16mm double glass is 2.04
If you want to know anything else I've been getting, please email me.