Just a suggestion for you:
Cut your cake strips a little wide to give him depth to help with the height so he won't topple over easily. Stack the cake with filling between each layer until you to get to approximately 3 or 4 inches in height. Crumb coat or frost then insert dowels (I prefer bubble tea straws because they are strong and easy to cut.) Be sure you have a 1/2 inch thick covered cake drum or board for the base of the cake. When you pick it up you don't want it to flex at all.
Prepare the next tier the same way. Use a 1/2 inch foam core board (instead of a cake board) trimmed to size and covered with press 'n seal food plastic. After you frost and dowel the second tier, stack it on top of the first tier.
Sharpened a long wooden dowel (or two) and drive it from the very top to the bottom of the cake and tap it into the bottom cake drum. The beauty of the foam core board is that it is so easy to drive the long dowel through and won't bend like card board will. It also adds height to your cake.
Hope this gives you some ideas. Others may have a better way.
Good luck! Can't wait to see pictures!