Waddy ... go here
https://www.facebook.com/schiltronwa...c_location=ufi
He gives a parts list and a step by step build report. You may have to click on a 'See more' link to expand the full report.
There's a good point raised in the later comments too ... Don't cover the arch in pvc tape. Allow the bare alloy to be better used as a heat sink for the LEDs.