Can it work?

Okay. Here is my room so far. it started out as a basic Shed with pretty much zero TL. On the wall we placed 19mm Planking and then plastered over that. moisture is being kept out by a plastic layer behind the planking. the floor is again initially just timber but batons along these timber Planks with acoustic foam and then tongue and grooved wood on top of this. to put it in perspective, the shed is about twenty feet from any other house incl our own. it's dimensions are 18"X12"X10" (@ Apex). the plan now is to put batons around the perimeter up tight against the plastered wall, then make a double wall consisting of the wall that's already there and a double layer of soundbloc, filling the cavity with mineral wool (btw what would happed if the cavity were not filled with acoustic wool?). then we are going to use these rubber buffer things, shown below to mount a VERY thick (18mm) Ply floor also shown below on as a floating floor. i havn't got the coefficients of elasticity of the rubbers but they are not completely rigid and are compressible on the surface only. as fas as i can gather they are made for impact (in fact, in particular on trucks where you have to drop heavy crates or loads. so i thought this would definitely dampen those unwanted mid bass vibes. i suppose the lowest frequency will be about 40 Hz, so the elasticity of these would want to correspond to a resonant frequency of at most 160 Hz. but i havnt a clue where i'd get that info cos these rubber things are made for a different purpose. on the floating floor will be a double Soundbloc-MDF wall (MDF on the inside to make it easier for airtightness later on). the inside room, we hope, will measure 16"X10"X7", pretty close to the Golden Dimension as an added bonus. I will worry about acoustics later though. now i would like to ask the pro's, am i for the birds? Or can this room work if i want to use it for a practice room/studio later on. I'm mainly concerned about the mass of the shed. i started out with the disadvantage of having an ultralightweight shed. but if i need to reduce the dB inside to 25dB outside at most and say i'll be pumping out around 100 dB at most, then i need a TL of 75dB. is this possible and can i make use of the fact that it's isolated in a 20m radius? thank you very much, any input from anyone who knows anything is highly appreciated. Overview: Soundbloc: Ceiling: Thickness of Wall: Outside: Window: Ply: Rubber:

sorry, i meant to post this in "construction"!!!!