I'm thinking about trying the "heel up" riding style, where the heel is higher than the toes throughout the cycle.

If I do, I would move the cleats up ;I have them back the farthest they will go, along with raising my seat a little (and forward)

I like to spin at a high cadence (no cadence meter, but probably 90~100+) since I weigh barely anything (just over 120lbs) - I thought maybe this will help....?

Any suggestions? Anyone ride like this? What are the pros/cons

don't.

What is your impetus for wanting to try this? My fitter called this position toes-down and that's how I pedal naturally. He said he would prefer an even foot with a smooth circle pedal stroke but I'm a natural toes-down rider.

I find high-cadence difficult but that's probably more due to poor cardio than foot position. I can now do a two hour ride with a 95rpm average according to my Edge 500 cadence meter but I am a sweaty mess when I'm done. It's definitely a challenge.

My advice to you is don't do it. There's a good chance you'll injure yourself messing with cleat position and pedal stroke if everything is fine right now. At best you'll be uncomfortable.

I'm 190 pounds so your mileage will vary.

I do this naturally, but only about half an inch. Should I be trying to level my foot?

If it's not natural, then don't do it.

Yeah, I posted then thought about it and had second thoughts.

I pedal toe down. So did Iban Mayo. But if you're not doing it naturally it probably isn't going to work without a period of adaptation and may not provide any benefit.

Ideally, you keep a 90 degree angle between your foot and lower leg