I have been looking at this. If you want to mess with it, I have uploaded a file painted_TEST_VERSION which has two extra physics sliders. I would be very happy to hear what you find is most realistic.
One is a multiplier for the wind force on the masts and rigging etc. I have found a couple of (not great) sources describing ships making 11 knots under bare poles in a hurricane. The 0.5a build would already do this. The default in the test build is to increase this drag by a factor of 1.5; you could partially justify this by saying that the 11 knots is presumably with no topgallant masts (or topmasts). Like this, the force on the bare poles is about equivalent to half the force on maintopsail.
The other is a multiplier for the lift force on all the fore-and-aft sails. It doesn't affect the drag. I have set this to 0.6.
These two seem to make it much more difficult to make any progress to windward under only fore and aft sails, while keeping the staysails still a little bit useful, and not changing the usual performance too much. But I haven't tested tacking etc. properly, and it's possible that there are still some of the effects I noticed while tweaking it, that when sailing with the wind on the beam you can go faster by taking in most sails behind the mainmast. Maybe this is realistic, or maybe it needs some tweaking of the hydrodynamics.