See previous page for Thomas's reply, which ultimately meant there was no huge incentive for a group buy.
I've started making a set out of 18G aluminium with a high quality rubber seal. Trouble is, even with free metal (from Rod the Vintage as a thank-you for some work I'd done), the seal was very expensive (£46), even dealing direct with specialists, plus I've probably been on them for five hours so far, and that has only got me as far as the blanks. The blanks, BTW, have taken about 3/5ths of a new 8x4 sheet of metal.
Overall, if you're slightly time-poor, I really would buy the Lokari ones, as you probably won't save much more than half of the price, but would certainly cost at least an extra weekend, in addition to the actual fitting time.
I'll report back when they're finished though, just in case things turn round during the later stages

. I still need to find a way of making the brackets, plus a way of joining the rubber seal to the metal: the Lokari ones use stainless wire to stitch the seal on.