Once you're past the danger point of boilovers, you could just add boiling water to the pot if you wanted to boil the full amount. This would be my strategy for IPAs and anything else highly dependent on hop utilization. For this particular beer, topping up post-boil is fine. If you use a 10lb (1.25 gallon) bag of ice instead of cold water, you'll chill much faster. With a partial boil and a bigger batch size, you'll lose some IBUs from the NB version. Assuming you haven't made your purchase yet, I'd switch the Goldings to something in the 7-8% range.
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