Just got back from Home Depot. About to cut the 2" ABS pieces for the top bulkheads, solvent weld those two in, then put the internal pipe and test caps in. After that, it's fill it up time!
7" from the top of window. I started marking the time with masking tape at intervals and found that over 10 minutes it filled 1.25" which is 74.26 gallons.