Guitar booth

Hello, I'm building a somewhat quick and dirty gtr iso booth out of a spare room at my studio. Its application will be to use it when I'm tracking live drums. The bleed through to the drum room doesn't have to be zero, but I will try to get it better than what it is now. The dimensions are: 11.6 ' by 7.8'. Ceiling is roughly 6.9' The drum booth is to the right, and shares an ajoining wall that is decently insulated. Most of the sound seems to be coming through the ceiling. Here is a quick diagram of what I'm thinking of doing. Basically, I'm going to insulate the ceiling with R-11, two layers. Build some Super Chunks in the coners and make some 2' - 4' 703 panels. I have the 703 and birch panels, just need to get some more burlap. I was at Groove Master studios in Chicago several years ago and they had stone on the walls of the gtr booth. Is it a good idea to go there, or just over kill? The room will be mainly out of site, only a guitar amp, or bass amp will be in it. Another hard spot will be the two large HVAC ducts that cross through the room. I purchased Duct insulation for that. I'm mainly looking to tone down reflections, not trying to make it %100 sound proof. Please let me know what you think of my plan and if you have any suggestions, please shoot them my way! I will be adding new pix as I get further along in the project. Here are some pix of the actual room. Thanks alot, Matt

Here are some pix of my guitar booth near completion.