I set up a triple as a 50/30 double once and it did shift. It didn't even shift that badly except that it liked to try throwing the chain, although obviously you're not going to shift under load. The only thing special needed about the FD was it did not have a shaped cage.

I would just run a triple though, the only reason why it wasn't run as a triple is the FD didn't have enough throw to shift all three rings.

If you want optimal performance, you should stick to ramped and pinned matched pairs of rings, within the spec ranges of the FD. There is a noticeable difference on how well things will shift.