If you have a free area you can stay halfwind to build up pressure in your sail and then you turn downwind and make your Run. Many speedsurfers are going 30°-40° off-wind, even more is possible (and very fast) but it becomes really technical. Sounds good, but there are very limited spots where you can go really fast and sail the course you like.
As you can imagine on this picture, which shows West Kirby a few hours later than the first one [Source: http://www.redsurfbus.com/], rolling chop can be really difficult to handle and forces a lot of crashes! Steve Thorp managed his big 50 at the beginning of his run, but the rolling chop made it very difficult to do just a good 10sec. run. Loosing control because of the chop is not the only problem, our speedsurfing equipment produces less vertical lift on broad courses which makes it harder to keep the board flying. Instead of accelerating the board starts to decelerate.
Rolling chop is a problem which you can get on various places, Southend and West Kirby are two totaly different spots but rolling chop can happen at both places. During the World Record event "Driven by wind" the riders had problems with the rolling chop at Southend and here is a good impression how Southend looks with rolling chop. [Picture taken by Steve Thorp]
Maybe there are some spots which you can use in superbroad and windy conditions without getting too much rolling chop. Vollerwiek seems to be one of this spots, the following pictures was taken in 30knots+ conditions and a course of 130° [Picture taken by Thomas Döblin], for me it looks pretty good, but I don't know what you get with 40knots+ and 140°.
A perfect solution for the rolling chop problem are probably curved beaches, but there are only very few ones. The second best option could be a windy course which is not superbroad.
La Franqui for example isn't superflat all the time but there are really windy days with 40+knots and the wind blowing 20°-30° downwind where the water is flat. [Picture taken by Hans Kreisel] In these conditions you can go very fast along the beach and sometimes you can bear of to get even more speed and a nice 10sec. run. Because you can do very high speeds on the flat course anlong the beach here it is possible to set very high 500m speeds, although nautical miles over 40knots are possbile!