What I've done in the past is cut out the thin metal part that connects the L/R sides of the Spas cage at the bottom, back end where it fits into the shroud. You need to spread the halves apart when you insert the 870. The strength of the Spas cage really grabs the sides of the trigger guard tight.
I also cut a small notch out of my Spas cage to allow the pump release lever to remain on the shotgun.
You'll need to cut the bottom of the trigger guard off, leaving the front piece where it comes down from the receiver. Don't cut off too much as there are parts inside the trigger guard that can keep the unit from working if removed!
There's some decent pics posted by Glenn in this thread:
http://forum.alienslegacy.com/viewtopic ... ght=tanaka
Russ
_________________
"A writer needs a pen, a painter a brush, and a filmmaker an army." - Orson Wells.
http://www.rookscastle.comhttp://www.alchemyarms.com