At a regatta I attend up here on Lake Lanier, they put the multihulls on the same course as the lasers, thistles, and optis.
The thing is that the optis were the last start - we were the first. We did our two laps and by the time we were finishing, the optis were in their start sequence. The finish line was like how it was during TW and so the 40 or so optis were lined up like ducks across the finish line while I'm doing 20 knots to the finish. Scary stuff.
The RC didn't even notice us finishing.
I'm not sure how your example applies to the Tradewinds having a seperate start finish line, or am I missing another point you are trying to make?
The example you've sited also sounds like a long standing dingy regatta that a few multi's got an invite for. We've all attended one of these and we all pretty much know what to expect. It's rare that a dingy PRO will fully understand the issues of putting multi's on the dingy course straight out of the box.
