chosen1608, sorry my friend didn't get back to you, so I will try and answer your questions the best I can ~ using information from him. First, we don't recommend using a single plate of plexi. If you do, slot depth will be determined by the plastic strip around the top of your tank; water will drop to the lowest level of the slots; and you want that to be above the bottom of your plastic ring, so it doesn't look like you need to add water to your tank all the time. The problem with a single plate, is that silicon doesn't bond well with plexiglass, so you are very likely, over time to get a leak in a single wall (then the tank will drain to the level of the leak ~ especially if power shuts off, which then becomes a major issue). Our recommendation is to go with a double baffle wall, similar to what is used in sumps. Measure 7" from the back of the tank on the side, and 7" from the back corner along the back ~ place a piece of tape at the 7" measurement on each wall. Then use a piece of string or tape to measure the inside distance between the two pieces of tape; that distance will be the width measurement of your first baffle. Measure the inside distance from the top to bottom of the tank, subtract a 1/2" to 3/4" (again depending on the height of the plastic ring on your tank ~ water level will normally sit about a 1/4 or so over that height), and that will be the height of your first baffle. The first baffle will be siliconed in (using aquarium silicon available from your LFS) sitting on the glass bottom of your tank. The second baffle will be the same height, but 1 and 1/2" shorter on the width (this will result in the two baffles being about 1/2" apart when placed in the corner of the tank). The second baffle will be siliconed in at the top of your tank (sits 1/2" off the bottom), so water runs under it and into the overflow chamber. Silicon the rear baffle in position first (using a wooden wedge under it to hold it in position ~ otherwise you have no room to do it, after the front one is in place), once it is dry, silicon the front baffle.
I hope that helps ~ if you need any addition clarification, just ask. Also, just so you know, you can purchase premade overflow baffle kits (they also have a double wall design)
