For securing the dropouts, I've had luck cutting a 1x1 inch piece of lumber to the dropout width and drilling a hole lengthwise for the QR skewer. You can also use a pair of old hubs if you have 'em lying about in your used parts bin. I've also used lengths of cardboard - cut to the inside width of the bike box, rolled up, and taped in place - to reinforce the cardboard box at strategic locations.