@shaun I just followed your exact steps using Mango Core v3.1.1 and Mango UI v3.1.5 and I had no problems. You have to replace adminTemplate in 2 places, make sure you get both.
Can you let me know your core and UI module versions, what browser you are testing on, and also open the developer console (Ctrl-Shift-I in chrome) and let me know if there are any errors in the console. Also try clearing your cache.
edit: I'm going to say again that we don't recommend taking this route, you would be better off using a custom page or the dashboard designer unless you have a need for a highly customized app and you are comfortable maintaining it.