OK, here is the solution.
1. Cut a hole in the floor of your coach about twice the size of the tree trunk.
2. Using quikrete or some other fast setting concrete, pour the hole full and sink your tree trunk down into the mix. It may take several bags of quikrete as you may be filling an entire bin. You may want to consider a mixer or truck as those bins can hold a lot on concrete.
3. Spray the tree with polyurethane or clearcoat (auto clearcoat works best) to insure that the tree stays green and pretty year round. (don't worry about over spray on furniture, floor, etc. I've found that the clearcoat is better than scotchgard on cloth surfaces).
4. Using a caulk gun full of liquid nails, liberally glue each ornament on the tree (make sure you wait at least 48 hours for the clearcoat to dry).
5. Finally, wrap the tree with several strands of christmas lights. You may use colored or clear, but at this point, it doesn't really matter...the effect will be the same.
If you find that the tree is to tall, or to wide, you can cut out a hole in the ceiling or break out a window if necessary...
Finally, top the tree off with a star or angel. Dramatic and permanent! Your bus will be the talk of the board!