I had a gas powered pressure washer (the kind with the "dolly" like handles and wheels to transport it) on the rear rack of my bike once. So It looked like I had a 5 ft sissy bar on the bike. I got some looks, that's for sure.... I'm with PJ, you could put a crate or something on the back but you wouldn't have much room for your woman. I throw my lunch box on the back of my bike in the morning and there's not much more room for anybody else (passenger wise, that is)
I currently have an action packer on custom mounts. It sits too far forward for a passenger. I have a diamond tread plate that I am going to use to offset the box back about 8 or more inches. That will allow a passenger and give me more room for bungee strapping my tent, chair, & bedroll behind me when I solo camp.
Well guys - here's what I came up with and it looks like it should work. For $6 I bought a hard plastic battery case with snap on lid at WalMart, strapped it tightly onto the back, then strapped a small cushion to that. She can't lean hard against it of course but it give her a little comfort - and my babe is worth it! : ) Thanks guys for your suggestions!