Jess is great!
I have seen real improvements in my symmetry and strength and I am sitting (in the saddle) better and more evenly. I work on my core daily as it is - but the detailed program is intensive; she focuses on isometric exercises that target specific riding muscles.
My muscles are very tight, so I do the pretzel at least once a day! My problem is keeping up with the material because I have to stretch for 90 minutes a day regardless, and then add the 30 minute sessions as time allows.
I also do Feldenkrais if time permits! If I do everything in one day (including cardio), it takes me about four hours – so I just can’t do it daily. That said, doing any of it is beneficial if you are reasonably consistent
I’m 68 years old, and due to all of this my DH thinks I’m riding better than ever in spite of my chronic pain.
I just signed up for her breathing course which starts in a few days - I’m very excited about it!
She does go on a bit, which can be somewhat frustrating – but she explains everything in great detail, including the biomechanics of riding and the detailed exercises - so for those of us who like that sort of thing it’s pretty perfect 
I just wish I could get my adult amateur students on board with this stuff – of course they’re all around 40 years of age and younger so I guess they don’t feel they “need it” – though they would surely benefit.