New studio build in large tin shed

Hi Guys, John, I signed up to this forum over 2 years ago with the intention of building a mixing studio. I have been reading up on this forum for ages and think I finally understand enough to get started and I am finally at a point where I have enough space, time and resources to put into it. I do have two design questions at the bottom of this post, but most of the post is construction related. The mixing room will be built inside of a large garage shed (12m x 6m x 3.2m) in a residential area, Western Australia. Shed is a simple 65mm x 65mm box tube construction with corrugated tin sheeting all round. No thermal or noise insulation. It has two large sliding doors on the front, concreted and wired with lighting and power points. The room will be built in the rear corner of the shed. I mainly just need a place where I can mix and be satisfied it will translate properly, and not annoy the neighbours too much. I mix Trance and Dubstep so the bass gets pretty heavy, my current neighbours have never complained about the music in the past 10 years, nor the grinding and hammering in the shed, but the lot behind the property (near the shed) is due for sub division and is bound to be filled in with little boxes with more neighbours to annoy. I intend on building a sealed room against the corner of the shed, with the layers of gyprock facing the tin, supported by a timber frame filled with insulation. The studio will then be built inside this box, with gyprock layered on the outside of the inner frame as well. For sound insulation, I want the outer frame to sit in between the two upright posts in the shed. These posts are offset from the tin by 65mm because of the horizontal centre beam in the shed. I can either have the frame sit against this horizontal post so the gyprock has an air gap between the tin (as depicted in the diagrams), or build the frame in two pieces so the gyprock can sit against the tin, possibly glued to it. This will create a true two leaf barrier, instead of the two leaf + air + tin. How much will this air gap and tin effect sound attenuation? Can I fill this gap with anything to bring it back down to two leaf? Each wall of the outer frame will be built on the floor, gyprock fixed to the top side then leant up, caulked, fixed to the shed and then insulated. I have studied the "Staggered stud wall construction" diagram and realise what I propose isn't optimal, since I can't stagger the corner gyprock because it is built inside-out and against the shed. Is there an easier or more effective way I could be doing this? I plan on using two layers of different thickness gyprock (16mm+12mm) for both the inside and outside leafs. I may be able to budget some plywood in for the build and replace one layer of gyprock for plywood for one leaf. I have taken John's small studio design and used sketchup to place it where I want it in the shed. I noticed I have room to make some adjustments if you guys consider them to improve the rooms acoustic performance. 1. I have decent height on this shed, so I can remove the bend in the ceiling and have it flat (but still angling up towards the rear). This makes construction easier and it gives me a little more room at the back for a raised couch. 2. I can do the same to the right frame, remove the bend and have the left and right walls symmetrical. This also means I can build identical bass traps on either side, plus give me a little more room. 3. Since I will have gyprock on the outside of the inner frame, this will make acoustic treatment for bass a little more difficult. Would acoustic hangers in the air gap between the leafs help low frequency absorption? What if I move the rear outer wall back a bit and put hangers there as well? Note, I also intend on floating the studio to achieve optimum decoupling between the leafs, this I have read a lot about and I think I understand how to do this. I still have a few details to figure out, and would appreciate some help getting this project off the ground. Budget is about 3K AUD.

use double 5/8s with greenglue with a room with a room design if dont have the space do staggered stud system. since bass is your problem ur gonna need a lot of mass n absorbtion. thats the only way