OSP... one thing to think about is what are you gonna do for the road trips you're talk'n about with Drewpy?
My recommendation, if your gonna chop off the sub frame behind the seat, and you're even slightly inclined in fabrication, create a way to mount a temp platform for your bags. Something you can take off when you want, but throw on for the long trips. doesn't have to be anything hard... just something that holds 50lbs or so. If you create it so it mounts and sits high enough, you won't have to worry about the brake lights as they'll be visible under the platform.
something like this...
