That is by far one of the more difficult covering challenges.

The way I do it is to cover the side of the fuse and fin, then put one or two slits in the covering in the curve area. make them close to the curve, but not quite up to it.

Now, heat it with a heat gun as you pull it down over the curve. the slits will help, but you need to be careful that the pulling soesn't rip the covering where the slits end.

I'd draw a diagram, but I'm on the road at XFC right now and don't have Photoshop