It all starts with a frame...

Cost of that frame? What is it? Where did you get it?

Hi @plonkster sorry about the delay to respond to your query.  Life happens around us and I had to take some closeup photos for you.  

The frame is home made and consists of lengths of lip-channel and flat bar.  The lip-channel is mounted horizontally and is screwed through the IBR into the brandering below with long Tek Screws. Then from top to bottom I ran flat bar fixed onto the lip-channel, also with Tek screws.  

To mount the panels onto that, I drilled holes into the flat bar and ran an 8 mm tap through it for the bolts.

Aaaah okay, not too far off my own frame then. Mine is 40x40 angle iron. The first frame was 5mm thick (seriously over-engineered) but I have since settled for the thinner 3mm type. Have a cheapie welder, but I learned that you can counteract the cheapness of the welder somewhat by using proper rods. Afrox Vitemax works well. Only thing to keep in mind, when you put aluminium on steel, the steel rusts, due to galvanic corrosion. So you want to put some insulation down, rubber, or bitumen strips. Unless you're in the karoo, then it might not matter ;-)

Did you consider wood in the place of the lip-channel?

Is the angle of your roof correct for your position of latitude?