j.d.,
Many people with a lot of free time feel your pain. Many of us would rather be in the gym more days per week. The thing is, you're at risk for messing up your linear progression if you try to do SS in a way that isn't outlined in the book. Most people that aren't on steroids aren't going to recover from much more than 3 days a week on SS once the weights start getting heavy.
There are other programs that allow for working out more days per week. If you are still convinced that you don't want to do SS as outlined, it would be worth looking at a pre-designed program that allows for more days per week.