Provided you know how to SUP foil on waves, there's two skills that are needed to be learned in order to be able to do downwinders:
1) pump and paddle your way up to foil with minimal push from the bump behind you
2) keep the foil flying after that by reading the apparent mess of an open ocean with 25+ knots of wind.
Obviously, you can learn the second only after you learned the first. Here's a short video of Eric Terrien explaining how to take off in flat water without any help from wind/waves. Good luck.
All this talk about foil downwinders also because today is the day of the Molokai to Oahu race. These are the foilers registered as of July 20th, but I know there's more of that.
Changing topic, yesterday the final act of the 2018 Maui Race Series organized by Hi-Tech was held at Kanaha in very windy conditions. Jimmy Hepp has a large gallery of shots here.
4am significant buoy readings
1ft @ 14s from 204° (SSW)
0.9ft @ 15s from 207° (SSW)
Small numbers at the local buoys, but still numbers. That probably translates into flat to knee high with the possible occasional bigger set. Not sure if I'll go today. If I will, of course, I'll report from the beach.
This is the best set I've seen at Ala Moana in 15 minutes while I writing this post. Other than that, flat and only three guys out. That should tell you how marginal of a day it is today.
3.6ft @ 8s from 91° (E)
North shore definitely not a good alternative for surfing.
Wind map at noon.
North Pacific has a small NW fetch associated with a decent low which unfortunately will move north. Small stuff (2f 11s on Thursday), but it will be nice to see something different than the usual windswell, which will continue relentlessly.
Nothing of relevance in the South Pacific.