Hmm, that might be a good question for an experienced builder, which is NOT me.
To me, two and a half inches sounds like not enough rake for such a slack steerer angle. You might need more rake. Without enough rake, there would be too much trail, which would make the bike handle sluggishly; and tiller would make it even harder to balance at low speeds. One other thing I notice is that the front and rear tires don't appear to be in the same plane. Is that just the angle of the picture, or do you need to straighten it?
The seat is fairly upright, and the seat is certainly low enough. So those two things shouldn't be problems.
Sorry I'm not being more help.