Every min for 21 minutes (7 rounds)
min 1 - double unders x 30-50 reps (cap yourself at 40s)
min 2 - Strict HSPU / BOX HSPU x 6-12 reps
min 3 - Kipping Toes to bars or GHD Sit ups x 8-15 reps

On double unders focus on relaxing your shoulders/hands and breathing during doing work.
We want to work pure gymnastic pressing strenght on hspu, so keep body tight and full extensions on finishing point.
On toes to bars try to be "tight" on right time, meaning once you have to kip and use your abs/hip flexors/upperback muscles do it, once is time to "relax" a bit do it. Remember to breath during movement and let it "Swing"