Hi Frozen penguin,
What you are doing make sense. I have a couple questions and things you might want to consider.
Are you trying to replicate the approximate breakdown of the total stock market, or are you purposely over weighting small and midcaps?
If you are doing the later on purpose, that is cool (it is what I do in a similar situation), however if you are attempting to mimic the Vanguard total stock market fund, your ration of SP500:Midcap:Smallcap should be closer to 81:6:13.
See hereDue to the market cap nature of the total stock market fund, it is heavily dominated by the large caps. If you think that's a problem and you want to fix it, what you are doing is good. If you want to get the same returns as the total stock market fund, what you are doing isn't quite right (but may or may not give better returns..).
One other thought: it looks like the total bond fund in your 401k has the same expense ratio as the admiral fund (or ETF) Vanguard Total Bond, whereas the stock funds in your 401k are slightly more expensive than the admiral fund / ETF Vanguard Total stock market. So if you were in the situation where you are maxing out your 401k and IRA and still had taxable investments, it might make sense to buy all/most your bond funds in your 401k and then IRA, and use your taxable accounts to buy the domestic stock fund. This would also be the most
tax efficient placement. Assuming you can do that while sticking to your desired asset allocation. International funds are a little tricky in terms of optimal tax placement, or at least I never figured it out.