We do not install electric, or over 12 feet (sometimes 14). For electric, we have a contractor that we refer that work to. It is a family business that has been around for about 70 years and all they do is electric.
In Florida, the moment the job description requires a ladder or electric, insurance rates climb astronomically.
As for channel letters, we will sell them, but the customer is required to handle the install with their licensed electrician. We will do sign faces.
Percentage wise, of any of that stuff, 10% would really be pushing it.