You know, before you commit on your shed, consider looking at many other designs and encorporate other ideas into your design.
Consider the gable roof. This idea lets you have an attic area for not too often used things and a lumber rack which really comes in handy.
Instead of using OSB boards for your sides, use Masonite sheets. will last longer. Also consider using 2 x4's 16 OC on walls and floors and ceilings for extra support. Encorporate double swinging barn doors with PIANO hinges instead of gate hinges. Piano hinges will ALWAYS work properly and NOT bind on you. Double doors are great for hauling in and out big items.
Floors, do not skimp on sturdyness on floors. I made mine with 2X4's 16OC and on 4 x 4 wolmanized skids for that off the ground look. Then use 2 layers of 1/2 inch plywood going in interlocking directions for a no bounce flooring. Over doo the flooring.
Run a dedicated electric line to your room with its own breaker. When you wrap up that amp eating tool, you do not want lights flickering and something inside going out. Beef up that breaker for that room.
On corners on the outside, use metal outside corner flashing instead of 1x4's. Use metal drip edges. Seal that puppy up and use metal where you can. The masonite will last a long time if kept painted and off the ground.
Get a good 4 in 12 roof slop. Use good builders paper and good shingles.
Remember, I can tell you this for sure and others will also. When you build your shed and get all the stuff you want in it, the size becomes too small and you immediately say, I wish I had made this bigger. Plan way ahead.
Install roof turbines on the roof and consider adding metal braces in the hole to prevent break ins.
Reinforce all areas for breakins. I would not install a window even though it lets in more light, but its one place for intruders to come in. Install three good hasp locks.
Plant rose bushes all around the building, or cactus. Its one good break in deterant. If your loading this with tools, consider how you want the doors to open. YOu may not want them to open so the whole street can see in.
In summary, shop around when doing this project and use as many space saving ideas as possible. Peg board one complete wall. this is great for organizing tools and space. Build that puppy full of shelves from top to bottom.
Also, on your roof eaves, do have a good 8 inch overhang so that the water will not bounce back up on your sides of the wall. Will save you some time.