Matt,
For this size, as a starting point, scrounge a wood pallet in decent shape. It will save you time and materials and should cost nothing. You can cut the extra 2' off if you want but I would just attach your crate 1' form each end which provides a buffer.
You want to isolate the base of the model from the pallet. You can do this in several or multiple ways. We typically do not put foam or skid mates between the pallet and the crate but some do. Depending on the model base construction and weight, use foam or foam squares between the model and the base of the crate. You DO NOT want it to be too rigid, a bit of bounce. Then line the crate in 1.5" white insulating foam available at Home Depot etc.
We do not use wood for single use crates, we use FalconBoard.
Water is possible, TAPE the crate seams or cover the model in case there are drips
Secure any parts that could possibly become a wrecking ball if they come loose. Remove or isolate with packaging.
Use do not stack cones either purchased or make your own.
Look up APMMM vendor SHIP AND INSURE.
We ship via FedEx freight but we are not overly sensitive to price. We want it to spend less time in transit which we think is less chance for damage.
You do not need to pay for a liftgate if you have people standing by who can lift the model into the truck. (or the receiver can unload.)
Good luck Charles