Construction questions for new studio build

Greetings all – I recently moved to Connecticut, and my new house has an old barn which my lovely wife has agreed to let me convert into a single-room recording / playing space. My intent is not to get totally crazy, but I’d like to keep the amp noise controlled to avoid neighbor issues. The barn was literally falling in on itself, so it had to be knocked down. That leaves me with a 16’x24’ foundation, which is the only thing present. It has packed gravel underneath a 10-12” slab. The footing walls are 42” deep, 10” thick, rising 8” above the slab. I’ve read Rod’s book, which led me here, and I’m currently going through Everest’s book to supplement. My basic floorplan is attached. The basic ideas are: - Double wall construction with a 2" air gap - Green glue applied between double layers of 5/8" drywall - Sill seal underneath both sills (int & ext) to reduce vibration transfer - 1 : 1.14 : 1.39 ratio for a main room. My basic questions, at this stage of the design process: 1. Do I need to float a floor? I’m thinking probably not, based on what I’ve read here and in Rod’s book. It’s a standalone structure surrounded by earth, though it does have gravel underneath to help control surface water (we're right on inland wetlands). 2. Can I build both walls up on the 10” footing walls? If I don't float a floor, I'm assuming it's the same as having the interior wall on the slab. But if I DID have to float a floor, would it be preferable to rest the interior walls on it? That would shrink my room, which is not ideal, but expands the airgap to 4" and allows for 2x6 exterior construction... tradeoffs, I suppose. I’ve attached a PDF of a floorplan I worked up in Illustrator, and my first attempt at working in SketchUp. Thanks all for the initial input, and to Rod for an incredible book! Best regards, - Kevin