I just fed my 110 and 130g babys adult mice. They took them easily. My 80g ate a hopper mouse real easy. I feed live by holding the tail with a pair of pliers. Squeezing just enough to hold the tail. That's my method that works for me.
Why? There's no need to restrain live prey.
In fact, using your method makes the prey more scared and therefore more likely to lash out and bite anything that comes near it.
Just put it in with the snake and let the snake do what a snake does.