Do you want your stocks to be only US or do you want to invest in the whole world? If the former then put it all in VTSAX. Of the latter then do a combo of VTSAX and VTIAX.
Same question applies to bonds as well. Choose with a total US bond fund or a combo of that and total international bond fund to invest in the whole world.
We invest in the whole world in a ratio of 60% US/40% international.