Insulation, Radiant and Vapor Barriers - Roxul installation questions

I'm going to insulate a basement home theater with Roxul to minimize sound transmission to the rest of the house. I have several questions:

1. One of my walls is 8" from the foundation. Should I fill this space with insulation (say fiberglass) in addition to the Roxul that will be between the studs (same question for the ceiling since the joists are at least 12" deep)?

2. My ceiling joists are i-type. Should I install the Roxul so it is flush with the sheetrock or will it be OK to let it rest on the lip of the "I" (in which case it will be 1.5" from the sheetrock surface)?

Any other "tips" appreciated as I've not done this before.
Thanks

http://www.quietsolution.com/Home_Theater_v7_scn.pdf

There are a variety of ways to accomplish a quiet room, this site is just one. What's nice aboiut this site is that it discusses the principles of sound transmittion. Insulation has been used for some time for sound control. Though it does reduce the transmittion of sound to rooms adjacent, it is usually around 60db. In comparison to an engineered application which usually starts at 40db.

Again this site is not the only site that can produce such results. Also the amount of sound transmittance is subjective depending upon the tolerance and preferences of the people involved. In either case it is always good to know the principles of sound transmittion so that you can best address the sound transmittion regardless of the application you choose.

Thanks for the URL.