I probably won't do the solar thing btw. I'm considering just putting polycarbonate roofing up there - do I need to orient them a certain way? And how do you best secure to the alumawood? Best to use the existing bolts securing the lattice beams downm punch holes through the polycarbonate roof and secure them back down on top of the existing lattice beams with the same bolts?
The polycarbonate panels I installed are directional. They have a coating only on one side for UV so you have to make sure you orient that side skyward. It says it all over the protective film that you eventually peel off during installation so it is hard to miss. Also, mine have internal cells that run the length of the panel and these need to be oriented so that any condensation will drain out with a slight slope. Mine came with detailed instructions you can print off for installation practices as you needed to use special tape to seal the ends that allow moisture to wick out but keep bugs and insects out of the internal parts.
They also come with special screws to use. They have a larger diameter boring shank to oversize the holes enough for expansion and contraction. I think you can get them for wood or self tapping for aluminum. The instructions also came with specific hole patterns to hold down the polycarbonate so I'm guessing you will have to punch new holes in the aluminum. Shouldn't be a big deal as the old holes will essentially be sealed over at that point.
When researching this before I installed them, along with many other things, I google up installation instructions first before purchasing as this gives me a good idea of all the accessories I need to obtain for projects like this. I've had mine installed for a month now and really like them on our greenhouse.