The leg kick, in and of itself, with respect to height is a minor thing to point cause and effect. But, it does have a contribution to make to your pitching cycle during the setup phase. In regard to your stride and other particulars, if the proportions of the rest of your pitching cycle are balanced out - to you and you alone, the stride foot plants, without much debate on your part.
I know I stated a lot of “words” to you that might not make a lot of sense right now, but I’d like you to try this:
Step 1.Don’t use any leg kick at all. Go through your normal “preferred” delivery motion and take special note of your confidence, you shifting momentum, smoothness in fluid of motion. Mark down in a notebook every single feeling passed on to your confidence along the way. What- why-when-how-come. If you can take video, all the better. In fact, take your notebook and go tick-for-tack with the video in slow motion. Remember to keep the pivot leg moving like you normally do.
Step 2.Progressively increase the leg kick up, then out straight towards your target. If you find yourself swinging the leg kick out in a circle, more than likely you’ll be landing either short - without much extension or off to the third base side if your RH, and off to the first base side if your LH.
Again, keep your pivot leg as a constant contributor to what you normally have been doing. This constant action - or lack thereof, by the pivot leg takes a variable out of the analysis, in other words trying to comprehend too much moving at one time. Again take notes and video if possible and review tick-for-tack in slow motion. See any improvement or lack there of? How confident do you feel as these adjustments take you deeper and deeper into the trial and error phase of figuring out what you’re trying to accomplish?
Step 3.You’re the only one that can determine if somewhere along the line you’ve reached your optimum cycle for delivering a pitch. By the way, very little should change between the full delivery and the set motion.
What I have described was used by myself to review pitchers coming back from back spasms. The lower back near the base of the spine and to either side can undergo a tremendous amount of stress during the early spring and autumn. Changes in temperature, sitting for periods on cold benches, cold concrete, not covering properly, a poor night’s sleep and other things can all contribute to back problems. Even worse for a mature man, more than for a youngster.
By the way, this “balance” remark by the coach who you talked with was probably an attempt to direct you to your most comfortable point in your progressive cycle. I honestly don’t think this coach was actually suggesting you to stop along the way, the proceed. On the other hand, I wasn’t there and not the beneficiary of your conversation.
Another suggestion, as your stride foot goes down the mound, try to visualize your foot smoothly sliding down the surface, not stomping on the surface with an emphasis on “umph!” planting the stride foot down.
I hope these suggestions help.