This was pretty much our biggest fear. A perfectly painted bonnet which needed to be accurately cut for a complex 3-D shape to stick through, without stuffing anything up. I am not in any shape or form artistic nor talented with hand eye coordination. I once made a matchbox holder at school which consisted of 2 pieces of wood nailed together and I couldn't even cut that straight. Dad did keep it, but I think because if he had it, no-one else could ever see it.
We made a template out of card to get a very rough form, leaving a lot of scope for expanding the hole later. We then used the dremmel for the initial cut, again keeping well within our markings and using lots of masking tape to protect against run away saws. Once we had this, we gradually expanded the hole using a metal file. It took a long time, mainly becauase I kept needing to lie down in a darkened room, but it did mean that we were in total control and could form the hole as desired.
Its shape on the right hand side evolved as we went along, and was initially going to be a straight edge, but the curves fitted beautifully over the airbox and also exposed the "Reverie" label. It looks quite nice even if we do say so ourselves! We finished it with a rubber edging strip from Clark rubber and job done. I can sleep once more....