Studio renovation - Advice sought

Hello, This is my first post here, but I have been lurking for a bit. Quite a wealth of knowledge and decent people it seems! :D I have a bit of a situation with the studio I work at. We are looking to increase our usable tracking space, plus provide additional iso with line of sight. Currently we have two studios seperated by closets and a storage space (see attached pic, grey area). The second smaller studio has been decomissioned, and all the gear has been moved to an "edit suite" upstairs. The rough pictures I have attached show what we have now (pretty close to scale on the insides of the rooms), and what we are thinking of doing. We have several issues: 1) The constuction of the existing rooms is unknown, although I know they were built with steel studs. One guy that was around when the studios were built seems to think there are three wall layers on the adjoining walls where the closets are, but he is in his late 70's and can't recall precisely. The owner/founder of the facility passed away 6 years ago, and all the "blueprints" were in his head, so we are flying pretty blind as to the actual construction untill we start making holes. 2) The ceiling height in the closet area is less than 10' as this is where all the ducting for the two studios has been run. 3) The area at the top of the drawings is a concrete filled block wall (with a doorway that will be filled in before building the new space) that supports the second story (bearing wall). 4) Construction space will be at a premium. Seeing as we have only one open face in the "cube", building walls and ceilings will be very difficult. 5) Cost... we have to keep the cost down as much as possible. So bearing all this in mind, this is what I was thinking... The second picture shows where I would like to take things, with windows looking through the four spaces. Obviously, the control room will not have line of sight with the other spaces but that does not concern me. To keep maximum space in the new room, I was thinking about the inside-out wall idea. Two layers of 5/8 on the *outside* of the new framing with no drywall on the inside. I could then apply fabric and wood slats over the Roxul Safe n Sound insulation to minimise any internal treatments. The questions here are: - Wood or steel framing? I am more comfortable building with wood. - 2 x 4, or 2 x 6 construction? - 16" or 24" centers? I was thinking 2 x 6 wood stud on 24"... but let me know if I am off base here. Building this will be a nightmare, as I may actually have to build the ceiling *first* then raise it up intact and build the walls underneath. This would be the only way to get fasteners across the drywall Ducting is in the way). If I were to build the ceiling last, I would have to slide the dywall over the top and glue it down instead of using fasteners. Keep in mind, the ceiling will not support anything but itself. Either way, I will not be able to caulk the two top exterior corners at they will be inaccessable. We have not started anything yet... just in the planing stages, but I wanted to run it by you folks to see if you had any suggestions. Oh, and please, no comments about the bad room design, or "three walls" comments... again, I didn't build it, but I have to use it the way it is. Once I get this cleared up, I will get some suggestions for re-doing the floors in the existing rooms! :roll: More issues there.... Thank you for your time and attention, and for such a great resouce. Regards, Dave Harrison EK Sound.