The TSP has very low investment expenses because it is utilizing index funds and the huge pool of dollars inside of the plan has allowed for the internal expenses to be extremely low. To give you an idea, the TSP offers index funds around 0.025% and these funds would cost most investors around 0.07% - 0.30%. The question to consider is the possibility of building a better portfolio outside of the TSP or utilizing other investment options to compliment the TSP.
Possibly from an independant RIA fiduciary. Best of luck!
TSP fund internal expenses are generally lower than most other plans