It is going to be difficult to get exactly around the numberboard with the decal dry. The best thing you could do is figure out approximately where the numberboards will go on the decal (lay it up as best as you can) and score an X on the decal so it can open up. Wet it, and float it into place. With a new, sharp exacto knife POKE around the perimeter of the number board so the decal has more room to break where you want it to. Dont panic if it tears, just try to line the edges back up. You will want some decal to be left on the numberboard. The goal at this point is not to get it perfect. If you drag the knife you will rip the decal. Once you get it flat-ish, and more importantly straight, let it dry. If it dries and it is not flat on the model around the numberboard, Micro-set (red bottle). Once you microset it, let it dry completely. Once its dry, go in with the knife and cut around the perimeter. If it dries flat with just the blue bottle then you dont need the microset, just cut the perimeter. Once its cut, you'll probably need to reapply the micro-sol (blue bottle) to be able to float the excess decal off of the number boards. Depending on how accurate of a paint match your maroon paint is, you may not need to be all that accurate with it. If the paint match is good, you can hide the edge of the decal pretty decently on a smooth, gloss coated surface.
Regarding the E, you can decal over a decal. Microset the stripes, let it completely dry and then apply the E. Let the E dry and Microset it again. If you feel nervous that the stripes may float when you do this, shoot the nose with a little gloss clearcoat to seal that spot, then put the E on.
could provide advice/ tips on how to do this as simply as possible so that the decals align properly on the loco
