Mike,
Page 21 of the Nacra manual shows the 16:1 downhaul:
https://www.nacrasailing.com/wp-con...al-Nacra-15-F16-N17-F18-infusion-C20.pdf I recommend running this into the front beam per the Falcon Marine Diagram:
http://www.theboatshop.be/Downloads/Falcon%20F18%20control%20lines%20layout.pdf You could also do a similar takeup system under the tramp which is what the A-Cat guys do. I do have a swivel block setup that gets you the required purchase, if you need it.
Sorry, I don't have any tuning information for the rig/mast rake. I would start with the mast rake around 5-5.5 degrees and the spreader rake at 50mm, these are common baseline for almost every boat I have sailed.
-Sam