Until the hooter is just as fast downwind as todays spis, I think it is a good thing not having to buy another sail.
Well you could get over this by restricting the number of sails that can be used at a regatta.
In the 18HT class the hooter is outlawed too and there is only one set of sails allowed that can be used at a regatta. If your sail is damaged then you have talk with the RC to exchange it.
The advantage of the hooter is in light winds, when the hooter can be used upwind.
The big ventilos M2 catamarans use those gennakers upwind in light winds.
