Bret,
I did mine in the wing cradles, exactly as you have suggested (seems to me this is much easier than after wing mounting). Be sure though (as others have suggested) that you get a good fit into the leading edge, including filing or sanding (I used a file) to get a flush fit between the surface of the wing skin, and the FG tip, if you plan to do this. What I found was that the position of the TE can be moved more than I initially thought by rotating the tip at the leading edge and filing small amounts to get a good looking fit into the wing LE. At first I thought I was going to need to split the TE as you mentioned, but the more I played with the leading edge, I got it to a perfect match with the aileron TE without splitting it. Also, I found that the final alignment at the TE was not initiallly fully evident until I had drilled a few matching holes with the skin and put in clecos, ie, pulling the FG lip tight against the aluminum skin all around can slightly shift the alignment. Not to worry, mix up some good epoxy and fill holes and redrill as necessary. If you are planning screws, the nut plates do the actual holding, so having a portion of the holes slightly corrected (oblong) neither shows nor matters structurally. It took me a couple of iterations of this to achieve a perfect TE alignment.
One more thing, on mine, the tip TE extended aft past the aileron TE by about 3/16". I trimmed this off with a belt sander. There was still plenty of "meat" left in the tip...enough that I don't feel additional reinforcement is necessary, but would be simple if desired.