Another way to fix that gap besides the "Revell always needs it spreader bar" is to shave just a touch off the wing mating edge on the outside of the undersurface wing half, you could cut the locating pins off too, if you need it. This lets the top half of the wing slide inwards a bit.
I see that it is too late for that idea, but, judging from the picture, you may want to consider doing both on any future build, since you look like you might end up with a slight gap after doing the spreader bar deal,,,,,after you stop the spreading even with the bottom fuselage part.
Nice to see another glazing putty user, I still use it because it shows up so nice while working, and the primer I use covers right over it in one coat, anyway.
Rex