I found that US Plastics is a good source for Teflon strips that can separate your canopy from the aquarium. Very easy to work with and will keep the oak from getting wet and turning dark over time.
Before you start you need to decide what style you like, what type of openings you want on your canopy. Some people use swing out doors, others slide off, and I saw on a post yesterday a company that uses piano hinges and the whole front flips up. Consider where you are going to place the aquarium and the types of openings that will work for you. Will you leave the back open for plumbing? What type of lights will you use and if its a packaged set of lights what are it's dimensions.
If it helps I don't have any drawings but here are photos of the one I just built. I used pine for the structure of the sides and back. Skinned the sides with 1/4" maple/birch plywood and used solid Maple for the front. The pictures are in the order:
1. Cabinet and canopy together.
2. Canopy with the doors open
3. Side of the Canopy. Originally this was going to be closed on the side but I measured the light fixture incorrectly. :scared: On the upside I didn't have to then cut out a spot for the fan.
4. The back of the canopy. We opted for an open back and open top.
5. Detail of the inside of the canopy for one side and back corner. You can just see the teflon strip that separates the canopy from the tank. That strip is hidden by molding.
A search on this forum will find you lots of pics of canopies.