From what I have seen with all of the tanks that I have the bottom is not at the bottom of the glass. The sides, front, and back extend past the floor of the tank. If this is the case with your 10 Gallon then chances are something is not going to line up right. Unless of course you have multiple tanks that you are willing to take apart and possibly mix and match it to work.
Have you made a frame for the new one? If you have you would want to glue that on as the last step. I don't think it has much structural value in a 10 gallon but I could be wrong.
If I were you I would use the bottom picture if you can do that. That one would look the nicest.
What are you using this tank for?