I am the Match Director for Somerset IDPA and we have been unceremoniously booted from SCFGPA in Bridgewater. I am working on another venue but in the mean time the match is dead.
On a brighter note, I am putting together another round of my "Intro to IDPA" class at EFGA on August 29th. I'll be posting details soon. I can run you through a classifier there if you decide you want to sign up.
On a semi auto shotgun the max magazine capacity is 6 (plus the one in the chamber). You cannot have a pistol grip on a semi auto shotty at all, no matter the capacity.
There are no restrictions on pump action. Pistol grip - OK. Enormous magazine - OK too.
I have a Benelli SuperNova with a 24" barrel and 9+1 capacity. The magazine is about an inch shorter than the barrel.