Re: Irimi/too slow problem
I'm 6'1, and about 230lbs. I'm interested in your footwork. Do you consider yourself "light" on your feet, or cumbersome? I've noticed that larger people tend to perform irimi as a large thumping step rather than a light, floating (or lunging) entry move.
When you enter, what is your back leg doing? Is it left behind? Sliding in after you? Or pushing off, to add speed to your irimi?
And as mentioned above, take note to when your hips start to turn towards uke.