Just Fly

I've seen a couple versions of this question on the forum, but not quite an answer I can digest.

I understand my UPT time counts towards total, time and that Solo can be PIC (but who has that data 25 years later?).
But looking at my 100 hrs of T-38 and 75 hrs of T-37, what "bin" do I log those? I assume SIC, but I've seen some dissenting views on that which I don't understand.

Using MyFlightBook to capture my mil records, and if I don't give my T-38/T-37 time either a SIC, PIC, or CFI checkmark, then the time isn't added to my Total.

Thanks in advance for the clarification.