A new TC combination that works well

One reason I have 5 (used to be 6) TCs, is that it always comes down to a per case basis - which body, which TC, which lens. No one overall answer as to what works best. Just discovered a suprizing combo that works well: 7D - Tamron SP 1.4x TC - Canon 1.4x TC II - EF 500/4. No tape on any pins. Smooth , accuarte AF. IQ? I did a series of shots using a monopod starting at wide open. Hard to tell any of the images from each other and I am picky. Might be able to go out an do some BIF tomorrow.