Welcome aboard Phil !
Ummm... I'm not sure I'd be doing a matrix as your first effort with pixels myself. I think I'd be trying to do a section of your display as pixels, then work up from there.
Taking in to account it is getting towards the end of September, you really don't have a huge...
+1 to OzAz
Troy is the guy to see, he's only just up north of Sydney if I remember right.
I've tried the cut it yourself method, and it's just a pain in the HoHoHo to do, and looks crap... cheaper and easier to buy the corflute cut in to props already.
As Benslights said, particulary if you haven't opened them yet, you can take them back for a full refund at Bunnings. :)
Although if this will be your first year at pixel lighting, it may not hurt to have some of your display using those lights, if not for anything more than filling up spaces...
I ran 60 pm, and I don't think you'd notice the difference in 32mm air seeder.
I'm planning on adding an extra arch this year, but drill holes in the back and put some bullet pixels in to it. I'm thinking with this one much further from the audience, they won't notice it..... looking around 15+...