Depending on his age, possibly a little too much in the C.
My father, who was a VP of the Bank of Boston, and ran their Funds, always gave me the adage of take your age, subtract that number from 110, and that's how much you should have in the C fund. Diversify the remainder between the S, and in later years (as the I Fund became available) the I fund.
I removed my TSP into a Vanguard account, with much much lower fees immediately after I left the FAA. I don't have the luxury of moving in and out of funds as easily as when I was in the TSP, but so far, I am well taken care of.
With that money and some other savings I have a dedicated advisor which charges me a lot lower percentage than the TSP ever did.