Thanks Jay, but my brother gets all the credit. We've been following the stay-home-stay-safe guidelines, so we couldn't work together on his.
Good news about the shipment.
I am building his crossovers. I bought a sheet of MDF at the hardware store to mount them on, and it was that cheap, flaky MDF that you speak of. That's no joke; it is so different from the MDF the cabinets are made from.