When taping boxes shut, make sure the box flaps tightly abutt each other, and tape all the seams. If you have two similarly-sized smallish models, you can get away with putting both of them into the same interior box. You can take several interior boxes, bundle them together with packing tape, and float them in the exterior box as one unit. Not masking tape or duct tape. Boxes that are roughly cubical or squat are the strongest.
Oblong boxes are less so, and flat boxes that open on their narrow ends least of all.
If not, don't ship it. A sturdy, tightly-packed cardboard box will support a man's weight.