I agree about the importance of a solid FB. I've tried converting TEs, fast OTs, power RBs, I mean everything. In a pinch, a converted blocking TE will work, but far and away the best thing to do is to look for athletes. I found a 4* athlete my 6th year into my dynasty and then a 5*
crusher at FB the next year. Combined with a good blocking TE and a power RB, my rushing attack was unstoppable.