Nice idea, having worked in a similar problem space for a number of years, I have some questions.

- How are you managing rebalancing, what might trigger a rebalance and how do you manage the tax implications of that?

- With a rebalance/deposit/withdrawal are you always a taker in the market?

- What's the custody side of this look like? i.e where do the stocks sit, are they in my brokerage account or are you custodian.

- How are you accounting for dividends in the portfolios do they get reinvested/included in returns?

- Can you manage all types of corporate action like splits, mergers, delisting, halts etc.?