Just had a training session last night with my regular training partner. Feels like I'm making some sort of breakthrough with this forward lean, it's like a simple but major piece of missing puzzle, especially for my FH. I've added a bit of additional tweak to my backswing as well. My coach told me to make my knee face a bit more to my right side during the backswing, and this allows me to put a bit more weight on my right foot, shifting my center of gravity a bit more to the right. During the forward swing the combination of the forward lean (it's really the butt sticking further back) and the weight on my right foot really allows my right leg/butt to drive the shot forward. Now I feel like my form is basically complete, maybe just some minor tweaks here and there.
On the BH side, it really creates a lot more room for backswing, but the more significant changes IMO were keeping the racket head pointed higher and also keeping the racket higher in general. This synergizes very well with the forward lean, although I had trouble achieving consistency once the pace increased, as the ball coming back becomes way faster. I think going forward I need to develop the ability to judge each ball individually and shorten the reloop action when necessary.
Here's a clip of my FH forms over the past few months. My work has been mostly on BH, but you can still see some changes. In the first section in April, I realized that I was rotating my body through the ball. This causes over-rotation of the body, resulting in slower recovery. By the August video I had addressed that to some extent by transferring energy to the arm at contact, thus reducing the magnitude and duration of body rotation without reducing quality of the shot. The last clip is from yesterday, when I managed to incorporate the forward lean and the increased weight on my right foot during the backswing.
Looking at the videos, I can see why my coaches didn't tell me to increase my forward lean. It's actually pretty hard to see from the frontal angle. I also didn't realize how straight my stance was until I watched my Oakland tournament videos, some of which were recorded from the side angle. It might also have something to do with my bad posture, which is usually a bit kyphotic, with a bit of a bend at the lumbar spine, so it looks like I'm leaning forward. But what's important is to lean forward at the hip and not at the lower back. What my coaches have been telling me instead was to loop more forward, which always felt a bit awkward. Turns out after I started leaning forward, my stroke naturally became more forward going.