I honestly do not know what Harry should so, but personally i would lose the upper body for a start, im not sure if he’s flexible or not but his upper body looks, restricting.
For me, you are right. Most of what i do is to try and get a big power/weight ratio ONLY because i cant do much else. If my surgery has gone well i will pretty much drop the weights and focus on core, balance, co-ordination, technique, mobility, speed drills, flexibility and prob more, i cant think right now. Im not going to kid myself, i have easily the required strength levels to jump far.
I think there are many secrets.