Showa Air Shock Mods?

I bought a set of Showa air shocks that are off a early 80's Goldwing and installed them on my Valk. I also found a Stewart Warner kit with a pump, gauge and controls to inflate or deflate the shocks while riding. These are 12.5" shocks which is what I was looking for since I run a 60 series car tire. I wanted to lower the back end just a little. These do the trick and I like the ride so far, my only problem is the bump stops inside the shocks are too short, so if you let the shocks bottom out the tire will hit the fender. I want to find out if these shocks are serviceable and if I can install larger bump stops? Or if there's a shop in SE Michigan that is capable of doing this.