Good luck with that. It was my understanding that the 1100 have an 8" tube coming out the back of the receiver at a certain angle, and I believe the magpul stocks cant be modified to support it.
The Magpul shotgun furniture is sweet. What kind of oversized safety did you go with? I've always bought the Scatter Gun / Wilson ones in the past, but changed after installing a Vang one.
EDIT: Just heard back from USDS. It's a Scattergun Technologies safety.
I painted the left side of the safety red with red nail polish - as they come totally black. I'm sure it'll wear off sooner than later - but I still need that visual reminder.