Completed the long overdue brake duct diy over this weekend. Wasn't too bad, took about 3 hours taking my time. Had to buy a few new tools (oh no) including a drill, some bits and a hole saw and an assortment of parts. The parts totaled about $200, add another $100 for new backing plates if you ever want to return to stock.
I'll be at Limerock for the PCA event this Monday to see if this makes a material difference. I fear my testing will be anecdotal as I don't have a way to measure a difference and my calipers have long turned black. I hope that at least these ducts help prevent cracking of brake pads, which has become a problem recently.
I got guidance on everything from the following post, although I think his duct mounting points were better located:
https://f80.bimmerpost.com/forums/sh...=brake+cooling