Have had this issue on a number of designs. What I do is run the lug up through the shrouds.
For this design, you can run a long one up through the BT-70, such that it clears the OD of the BT-60. A second lug would be needed through the shrouds just above that. Trimmed neatly, flush against the shroud, and they look quite nice.
We do this on the Nantucket Sound, Decim8 and the upcoming MIRA kits...
That comes back to the same question again, though, which is: how much does it matter that the forward lug will still be behind the CG?
If we don't care about that *at all*, then I could just put a single (long) lug on the rear BT70. If it's OK to be behind the CG but we want it as close as possible (how close?), then there are a few different ways (including the scheme you're suggesting) to get the forward lug into/onto/around the forward shrouds. If we *really* want the forward lug to be at least at or in front of CG, then we start moving down the list to the more difficult and/or uglier solutions.
If I fiddled with the design and made the forward shrouds further forward, then I could possibly get the point where they are close enough to the CG that I would stop worrying about it. Have to see if I can do that without screwing up the proportions of the design.
If the forward shrouds are an acceptable lug location (either in the current design or the above-described modification) then I could also do something like this:
Here, there's a standard lug on the BT70, and a wire loop anchored to the centering ring at the middle of the two transitions. Alternatively, the forward one could be made longer and glued to the side of the arch fin (like what Ken suggested):
Here I made the forward lug white just so it's visible in the picture.
I had been trying to get the forward lug more forward, but if I don't need to then there seem to be several reasonable solutions.
All this staring at this design and it's making me want to tweak some details (particularly the paint scheme), but I still like it so far, I think.