That's great to hear! Just one word of caution. You say "the feeling is that there is more power in reserve to hit much "harder"". In my opinion, trying to do anything in golf "harder" doesn't work.
A better thought would be to do it "quicker".
For the longest time, my handicap fluctuated between 2 & 4. My game was fairly consistent. I would throw in an occasional 71-72, or 79-80, but for the most part, I was 74-77. Up until about 1 1/2 years ago, that was my game. About a year and a half ago, I started "taking something off" my swing. I remembered something Curtis Strange said a while ago. Speaking about touring pros, he said that
"99% of touring pros swing at 80% of their capabilities 90% of the time"
. My swing was sound enough to play at the level I did, which isn't bad, but I figured that was as good as it was going to get.
About a year and a half ago, I slowed down a little. Because golf is a game of timing, I found that by slowing everything down, I got the timing right more often. I started hitting more good crisp shots and really didn't lose much distance, and started to become more accurate. What it also did was make me realize that if I was always swinging at 100%, I was really limiting my options. If I was always swinging the club at 100%, and was in between yardages, my only viable option was to take more club and try to swing easy. But not being the sharpest knife in the draw, sometimes I would take less club and try to "jump" on it. More often than not, I wouldnt hit it good. No wonder...if I 'm swinging at 100% of what I can control, then trying get a little "extra" out of a club requires me to swing at a speed I can't control.
When I say I slowed down, I slowed everything down. The timing is the same, it's just slower. So now when I need to get a little more out of a club, I'm able turn a little "quicker" and still maintain the timing of the swing. Most high handicappers, swing with their arms, and when I hear "harder", I think of trying to "muscle" it out there. Good players turn their hips and shoulders to swing the club. If you can maintain the timing, you would turn "quicker" not "harder" to geneate club head speed.