SearchMan, I replaced the tiny stock gear with a fiberglass one from the local hobby shop, opted for slightly larger litefoam wheels and kept the stock wheelpants. The .72 swings a 13 x 6 with good clearance and looks even better on the new SE gear legs. Balance was like yours after the larger rudder added some tail weight. Now it will knife edge the length of our field and hover till you get tired, but it won't climb enough to do a knife edge loop. - Just not enough side area for that.

Swaped the small tank for a 10 oz. one to feed the thirsty .72 so there went the tail weight gains Still the answer to the original question ended up 4" for me.

quint