luffing another boat downwind

Well in a Laser 4000 I'd have to bear away more than 40 in the sort of conditions we sail in on the Medway sometimes.  But to come back to passing people to leeward.  Sadly fast asymmetrics are fast in plenty of wind but in a wind shadow they can be slower then some quite slow boats.  hence I have a guideline you might like to share.  If its windy pass to leeward, if its not windy pass to windward.  Make this decision early enough and you can get enough separation from the slow boat.  With a big asymmetric like the 4000 I have to be very wary of the smaller (none apparent wind) boats like an RS200 or Laser2000 because they can luff even in the gusts.  Similarly to pass to leeward of a boat like a Wayfarer requires quite a lot of separation since they have a wind shadow equivalent to a block of flats!