Honestly, I would say go for the 3.5 development as well. Gold was released recently, and I'm sure everyone will switch him soon enough. Plus, having a hack like this only available for 3.5 will force people to upgrade to 3.5, which is a good thing.
I was nervous to upgrade at first, but I can't wait until I get my 3.5 skin ready for launch. I don't want to work on 3.0.X anymore.