Just packed up my D-55 to send to Fixit using the Aeris packing system form Stewmac. Admittedly more expensive than recycling a used box, but I think well worht the price. If you're not familiar with it, here's a video link:
Might be hard considering all the different sizes for amps. Maybe just one or two for the most popular sizes.That’s my go to shipping system. It’s expensive, but I feel that it’s well worth it. The guitars always seem to be kept in place and secure. I wonder if they’ll ever make an amplifier version.