I haven't "changed" anything about my bass drum playing. I play the same way now that I did 10- 15- 20 years ago. What has changed is the body and how it wants to accomplish what I'm trying to do. I certainly haven't changed it on purpose because I found a better way.
Flat foot is still heel up. I use that term because I don't angle my feet. The entire surface of my foot hits the pedal at the same time. It's the same thing that everybody I've ever seen play a bass drum does.( accept for the heel down players) Maybe the angles are different from player to player but at the end of all of that.... is still only one "techinque".
Again dude, I just play the drum, no tricks, no specific techinque, just play and find what works for you.
Maybe you haven't put much thought into this but I've been working on DB for 20 years. And I'm where I'm at because of that....not because I found a better, more efficient way.
If you want to become faster with the kicks.....find some songs like "angel of death" or "rapture" and play them 25 times a day. That's a great "technique" and that's what I did.
As far as Moeller, etc.... I don't find those to be "techinques" but NATURAL motion that your body does when adapting to moving forward.
If you apply everything you know about physics and natural motion, you will come to these conclusions on your own without someone telling you to do so. Techinque is just a word, not an application.
Your body will tell you what needs to be done to accomplish your goals....if you listen to it.
Cheers.
D.