Frank,
Scary moment, huh.
Are the engines supposed to be zero-zero-zero? Many full scale twins use asymetrical thrust lines for the engines to help in single engine situations.
If these are supposed to be zero, then here is what I would do: Attach one nacelle, then do a full measuring job again before mounting the second unit. If you can get one of them square with the wing, it should be easier to get the second one to match. Think of it as doing two single engine planes. I sure wouldn't try to do both of them at once.
I don't see an incidence meter in your shot. I would have one of those on the wing the whole time to make sure I don't bump anything out of line. I also have three or four angle meters that double as squares. These get placed at strategic locations while I'm mating the major pieces together.
Actually, if this was my plane, I would sit and think about it for another week or two, just to be sure I didn't forget something.
It always takes me a couple of days to mate the wing and fuse on a single engine stunt ship. Twin engines equals four times the work???
Best of luck,
Ron