Lovely.
I am not sure how you'd like to use the two 10 gal?
I'd make a cut out in two side panels and joint them for twice the length and the same width. I'd leave a substantial area of the glass to act as the middle brace, just cut through enough for fish to cross easily from one chamber into the other. This may make it interesting too to see how fish will utilize two distinct chambers.
I am not sure how you'd like to use the two 10 gal?
I'd make a cut out in two side panels and joint them for twice the length and the same width. I'd leave a substantial area of the glass to act as the middle brace, just cut through enough for fish to cross easily from one chamber into the other. This may make it interesting too to see how fish will utilize two distinct chambers.