I really like that unbury.me tool. I’m glad you found it too, @mmgalliv.
For a great modeler, it shows up really far down Google’s search results. 
Another Update…
I cleaned up the template some more. You can get the latest master here. The newest version adds back in the cumulative interest calculation. It also defaults to 30 years of modeling (though this can be changed in the hidden area to improve performance).
If anyone is willing to vet it (with a manual sheet insertion), I can move into the Tiller Money Labs add-on as the master. 
I think we are getting close.