Trombone squash harvest size as summer squash

[gorbelly]

After a late sowing, I'm starting to get full-on flowering on my tromba d'Albenga squash. I've read around that people recommend harvesting it if growing for use as summer squash when it's in the foot-long range. Really? The unfertilized fruit part of the female flower buds is already over around 7 inches long even before it blooms! If you've grown this before, at what size do you harvest it?