Move the X-Carriage over to the low side before you do this. Saves it sliding down and slamming into the end stop as you tip the box up, obvious but easy to forget.
You can string together some cable ties (not the ones from the BB parts, just cheap junk) and use them to hold the carriage in one corner, until you've finished all the fiddling around and are ready to fire up the motors. One of those things that I wish I'd thought of one minute earlier
