That's a tough one. We have to balance our efficiency of our serves to our style of play. If we drive into the court and hit it real fast, we end up 3' inside our baseline, not a great position for baseline tennis. Good for S/V, not so for our strong groundstroke games.
And hitting a "spanish style" serve, one where we stay atop the baseline after our followthru, we seldom win any easy points off our serves, needing to run back and forth along the baseline multiple times just to win ONE point.
I can't seem to hit Roche's style of serve either. I'd rather back into my serves with an extremely closed service stance similar to yours, and rush net.
But I KNOW I'd be more efficient with a more neutral stance, and get into service line position quicker and with less energy using old Roche's stance.
Your serves look into the 110's now, so barely slower than before. Given another 6 months, and 3" of growth, easy into the 120's, with your current stance and steady practice.
It's just that I hate the service stances of all the ex college players who are on the futures circuit nowadaze. Just overly complicated and not efficient like the serve techniques of Ferrer, Hewitt, Ferrero. Those guys might not have the biggest serves, but do have the biggest serves for their size.
Seems AndyRoddick uses less torso twist, but more stomach crunch, to get his power. But he's also an ape armed specimen, and one of a kind.
Wish I had an answer for you, but you'll have to experiment with your stance and swing to keep you power, and to uncomplicate the motion.