So a 10-12 PSI loss across the filter is good with you? Not me. That’s a big restriction before the oil gets to the engine.
Like I said, no GOOD header will take a long filter without that adapter. Even your over rated TTI header can’t take a LONG filter without that adapter.
I've always run the biggest filter I can fit. I run the Motorcraft FL299 2 quart filter on the Valiant and on my Ford truck. More oil is always better.