Gary,
Given the strength of, and the length of your existing lug, my "ancient rocket wizard intuition" says you will be fine. As Babar says, it is not ideal, but I've built enough odd stuff to believe your existing lug will work just fine.
One problem I've experienced with lugs that are too far back is, the upper section of the rocket can tilt away from the rod and you risk having it bind. I doubt that will happen in this case.
In my studied opinion, you can fly it as is, as long as you use a motor with a little "kick" (no E9s)