Well, I wanted to offer an explanation by seeing the Japan T2 as an easy way for normal people to upgrade to T2 standard. In this case/phase that meant swept wing, more dihedral and shorter tail. As you wrote before, Ed soon realized this to be wrong, and even though the Japan T2 flies quite well the final T2 is noticeably better. If Ed had reduced the dihedral further he would have had an even better ship.
A more technical explanation could be the symmetric airfoil. Due to the absence of down pitching moment quite small static stability margins are practicable, and they are desirable for neutral flight behavior. But this in turn might require a longer tail and shorter nose for better damping. (Still have to check that.) It was no trouble to take the carrier fuse and put a few balsa strips on the wing saddles to make the pusher wing fit. And seems Ed completely stopped building after the sad Simla affair.