What you wanna do is cut a shallow route lengtwise on the top of the pickup to accommodate the "chrome bar" on a toaster cover. The black, textured plastic wrap on a HB1 is roughly 1/32" thick, so I don't think you'll need to go much deeper than that, i.e. into the reddish epoxy stuff underneath it. Even if you need to go a bit deeper, rest assured no harm will come to the coils. Now I'm not familiar with the English names
of the precise tools required, but unless you're really handy with those you should commission a professional to do the job. Cheers! 
