Did a temporary mod to a cheap set of RCA cables... opened them up, stripped the three wires, crimped them to some female pin connectors, and plugged them into the back of the TG16. Fired it up, and man what a difference! I never remember the picture being that clear, even when brand new! RCAs vs RF... there is no comparison!
Eventually, I'll do a permanent RCA mod, but in the meantime, this is functional enough so I can continue to play the system. When my PC Engine Duo arrives and I get started playing Dragon Slayer (and I won't be using the TG16 as much), then I'll permanently do the RCAs
Thanks for all who helped!