Knees to elbows are tough for some people. Toes to Bar are as well. Here is a great video with Again Faster that might give you a few pointers on how to get a better kip out of the K2E or T2B. having said that, if you don’t have the upper body or torso strength yet to get there, practice those V-ups with fingers touching toes and atomic sit-ups to get you there.
5x 3 Pullups
10 Ring Dip
20 Walking Lunge 30 Floor Wiper
20 Split Jump