No experience of this system, but I thought I'd pitch
My thoughts would be:
If the symetrical is a skinny shouldered reacher, then the sail shape should be OK and gybing should by a similar exercise to gybing an Asymetrical
If the symetrical is a broad shouldered runner, then it will cause a lot of heeling, the sail shape will not be good and the luff will be difficult to control - just like when you go pole forward and try to reach with a running kite.
There are two concerns that I'd have with this system:
1. chafe on the headsail
2. Substantial point load on the forestay