I have shipped several heavy or odd shaped items, I have quit buying boxes for the larger stuff. Boxes are expensive if bought individual and in specific sizes.
For just odd or large shaped items i make my own boxes out of Masonite paneling and nylon reinforced strapping tape, and then wrap it in the brown shipping paper. Some shippers ( ups ) charge a Sir charge if items are shipped in something other than cardboard.
I have shipped a few car engines using the same method, first making a crate and a frame out of what ever lumber I had laying around then cover it with the Masonite and tape the seams.
Even if all of the items are bought; 1 x 4's or 2 x 4's, Masonite, screws and tape the box should not cost over 20 bucks, I don't think the shippers treat a wood box as rough as they would a card board box just because it will break.
Later
Mark