Cant answer your question as I dont know your age and need/tolerance for risk, but obviously those 3 funds in your IRA are excellent choices, just need to find the right mix. My bond and international allocations are higher than yours, for example.
My question for you is, where did you find an S&P 600 fund for only 0.05% ER? I prefer that index over the one that VGs small cap VSMAX fund uses, plus, VSMAX really isnt small cap per se, and their S&P600 ETF, VIOO, which is really good, carries a 0.15% ER.