haha, i tried to stack 2xtc + 1.4xtc on my 300, not only does it NOT AF, it gives funny error msgs too..hahahaa!
your shots are decent enuff for a 1st attempt!
try using mirror lockup + remote release?
I find that even on my 300+2x combo, anything slower than 1/80 requires mirror lockup + remote release to obtain optimum results...