sound on my PC is so terribly bad that I simply can't understand what Stuart said. So I'm afraid my 2ct are more reiteration... (if not, hope not too contrary...)
So, what drills should I try to educate my left arm a bit more?
First to fourth more a mantra:
- Relax my recovery-arm
- Relax my lower recovery-arm more
- Relax my fingers even more and paint a wide half-circled line
- Let my elbow lead the recovery as wide as possible from my side as far as possible to front, then let my relaxed lower arm dangle a little bit more forward to mailslot.
You are reaching very far to front. Might be you should imagine your mailslot just near your ears... and a video might show it as just right in front...
MC-Tracey recommends to imagine a tattoo on your elbow (if you're staying upright and your arms are hanging relaxed, the tattoo is looking outside). This should look forward all the recovery time until it drops into the slot.
To get back to this, you might even swim a lap with recovery-elbow still in water and lower-arm dragging behind the elbow, next dragging hand, dragging fingers have been Terry's "standard stroke"...
What I feel my self sometimes, when becoming aware of a tensed recovery is my tensed lower back starting to become a banana-shape. I think I can see it with you one and than, but I can be wrong. In this case an aligned straightened spine (little more tension into the butt) with relaxed head/neck has to be ensured forehand. (Before recovery can become relaxed again.) It might be worth to even have a look, how a more rotated stroke will help to relax your recovery arm up to your feeling the recovery happens more with leading elbow in front of your body than aside. (Not so much that you're starting to sink too much...) You should do some experiments with...
You're afraid your rhythm might becomes upset. Sometimes an improved stroke requires a new rhythm... But before working on that I'd recommend to work several laps with a TT. Start in slow tempo like 1.40s and then tweak it down after every lap with 0.03s...
When does your feeling start, the rhythm gets upset?
Or vice versa, start with 1.10s and tweak it slower every lap. When do you get the feeling of a significant more relaxed recovery arm?
Are both times the same?
Is the feeling right and left the same?
That's it for the moment. Enjoy your work!