I'm sure others have done it before, but we don't use the staysail downwind.

We either use it in lieu of the genoa in 28+ knot apparent winds upwind or just going upwind along with the genoa. The latter sometimes allows approx. 10 degree higher pointing angles, but not always. Keep in mind I have a 54 and not a 55. Just give it a go and see how the boat responds. I will tell you that you don't want the baby forestay (or any standing rigging really) flapping about.

--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com