Is there competition? If not, did run a Weighted Guidelines? If there is competition, you cannot question fee unless it falls over the statutory threshold. By running a weighted guidelines, it will give you a good starting point for negotiation.
I am wondering if I award a Time and Material base ID/IQ contract, that when I have a specific task order to let, that I could request a quote for the specific SOW, and request a FFP for that order.