My 2 cents: This is a lot of work just to see it in action. I have to click, fill out a form to save a scenario, then start entering data. I can understand why it was built that way-- it makes sense from an engineering perspective to do so-- but it creates a significant obstacle, especially when there is very little insight into the mechanics of the model without going through all of that work. In addition, the data entry UI is a bit confusing, even for someone familiar with finance.
Would suggest:
* describe what the "black box" does if one bothers to enter all their portfolio info
* make several predefined + pre-populated scenarios that a visitor can choose from list in <= 2 clicks. You could even just dupe allocations from common investment profiles such as one might see in a 401k option or when choosing from typical passive ETF/fund vehicles
* make the above step "dupe" into a new scenario that the user can then edit/tweak to their preference
