If you have a local Commercial GH supply company around you, you might want to check with them first. My local co is the cheapest place to purchase twinwall, and they sometimes have odd cut pieces which are too small for a big GH, but would be fine for replacement HF panels. The twinwall is easy to cut at home (hand saw, electric jig/scroll saw, etc)

There's nothing like that close to me, Steve. With the price of gas, catalog shopping is my best option.

Same here, no polycarbonate suppliers anywhere close to me; I have to mail order and pay for shipping.

Veggievicki, just a heads up. I don't know which size HFGH you have, but on the 10x12 it can be tricky to use panels thicker than 4mm on the roof, because anything thicker than 4mm that will not slip into the groove that accepts the top of the panels at the crown of the roof.

I think the panels that fit into the door frame, and the roof vents, might also be a problem in this regard...if you order 6mm or 8mm polycarbonate. Not saying it couldn't be defeated, perhaps by crimping the thicker panels slightly at the edge (??) but I am a little concerned that some parts of the HFGH frame are only designed for 4mm, so you might have to find a creative solution for that problem.

The panels that go on the walls could be any thickness with no problem, since they just sit on the outside of the frame. It's those pieces that are captured in grooves or channels that you might want to check.