[jjmaxwell4]

Complementing a Direct Index US 500 portfolio with Small Cap or International ETFs is very possible. You can exposure yourself to US Small Cap and International through ETFs - there is the related ETF expense ratio in that case.

[elil17]

Sure - but now that's looking like a lot more work and you're not saving much money. VT is 7 bps but VXUS is 8 and VB is 5. So if I want to use double just for my US large caps, I've got maybe 40% of my money there, 20% in VB, and 40% in VXUS. Then I wind up with a blended expense ratio of 4.2 + $1/month. Okay, I've saved about 2.8 bps, which is $28/year on $100,000.

In return I don't just have to do manual rebalancing - I have to move money in and out of a separate account every time I want to rebalance. I also have more tracking error.

I don't think that's something anyone is actually going to do for less than 3 bps. But of course if you are able to use Double as a one-stop-shop, then it's great.

I'll absolutely be keeping an eye on them and would seriously consider moving my money over if they could track MSCI ACWI.