Ceiling Question

Am planning to build a practice studio, converting the 3rd bay of my garage. Will be doing some recording, but mostly to create a scratch recording (vocal, AcG and maybe some drums) to click for later use in a proper local studio, correctly built with all the gear (not mine). Dimensions are : Length 4.2m, width 3.6m and height 2.4 to 3.0m. The question: the ceiling on the first .6m on either side (width-wise) can only be 2.4m high, but the center 2.4m (width-wise) can be 3.0m high. Tried to draw in SketchUp but couldn't figure it out. Essentially the roof line would be like a top hat. Hope this makes sense. I've read that taller is better, especially for drums (of which we have 2 kits), but not sure if the varied height would do funky things with the sound. Would it be better to go 2.4m for the entire width, or add the extra height where I can? Any advice would be appreciated. Attached picture is pretty close to what we'll build.

Here's what the outside box would look like. Hope this helps illustrate the question. Thanks.