At the Etchells Mid-Winters Regatta the PRO Dave Brennan is trying out a Windward Gate. After initial problems, including a head on crash between a Port and Starboard boat, he's added offset marks. Read these articles: Etchells Racing Saw New Courses with Windward Gates and Spindrift: White Rats
If the marks are far enough apart there are no special rule issues to consider. Each mark will have his own two boat-length zone. A distance of five or six lengths should suffice. Fleet racers might have some initial problems with an unfamiliarly starboard rounding, but that's it.
Next years revision of the zone to three boat lengths, means they have to be at least seven or eight lengths apart and if the SI so prescribes, with a zone of four, at least ten.
For any RC the trick will be to get the angle right. Both marks at the same rung of the ladder.
I would like to know what protest where heard regarding this windward gate....