Thinking about this on the drive in from work.
Consider a single 12" diagonal overflow in the corner with 3-1" bulkheads. Laid it out on paper but since at work don't have a 1" bulkhead in front me so guessing on footprint for nut and flange so might be able to go smaller. The bulkheads would be drilled 2 on the diagonal face, 1 in the back corner. 2 of the bulkheads, vertical standpipes for Herbies (primary and emergency) third bulkhead for return.
With this the 1" return allows less restriction, the Herbie give a silent overflow with a backup drain.
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