Is THP worth it for me.

I'm a volleyball athlete. I've consumed thp content for almost a year. My training is based 100% on their content and I keep up with John's new content on his channel. I've only gained about 2 in. of vert in the last year though. I'm curious how much getting on there plan would help me. I'm at 30 in. max vert currently. How much do you think realistically I could gain by getting on their plan. I'm 19 yrs old 6' 2" 180lbs. I'm also curious if any of you guys on thp think it's significantly better than just doing your own plan based off their content. How many in. does a mid level athlete gain by getting their plan.