Hamstring Flexibility Exercises and related activities

I studied this video by Range of Strength


I decided to adopt the following hamstring flexibility exercises:

Wall Tibialis Raise - B tier - as part of warmup for all training sessions.

Supine Hamstring Stretch - C tier - as part of warmup for my calisthenics and Sore Joint Solution sessions

Split Stance Stiff Leg Deadlift - A tier - as part of cooldown for my KB sessions. I found the weight of double 16kg kettlebells was not enough pull my torso down into the stretch. I still have to engage my hip flexor, quad and core to initiate the stretch and hope that the KBs provide assistance.
I'd like to eventually try the S tier exercise Straight Leg Deadlift but I feel like I should work with the Split Stance Stiff Leg Deadlift first.

I also started working on the Side Lying series in Geoff Neupert's Sore Joint Solution program. To get to 30 breaths per side I adopted a density training idea from the RMax days - do 60 total breaths per side, per session, and start with 6 sets of 10 breaths. Over time I will increase the number of breaths per set.

I also started practicing the hollow body hold again. Last year I worked up to a 60-second hold. Nowadays my max hold time is nowhere near that. The main reason I started working on the hollow body hold again is I notice that my shoulder flexion improves as I practice it.