I agree that high round kicks are powerfull, I saw a few landed this weekend at the 38th Annual Bando Full Contact Kickboxing Nationals
(the Oldest Full Contact Kickboxing Event in the States) in Columbus Ohio. Therer were Bama Lethwei fighter, Muay Thai fighters and even a Kymer team fielded fighters.
Beware throwing your weight too high while pivoting the support foot, this can easily cause the support foot to slip out from under you. I nice high knee lift is great for high kick positioning, just try your best not too be too light footed on the support foot while pivoting attempting the high round kick, this is the common mistake made in trying to kick too high too soon.
I would have to disagree with a previous poster who mentioned "Your kicking leg should never really be bent in the first place either. Obviously not locked straight, but you don't want it bent like your throwing a knee."
IMO, you do want to throw the high round kick just like throwing a round knee strike. This is just how my Bando (Bama Lethwei) Instructors and others teach it. Throw the knee with pivot into a round knee strike and follow with the shin, instep.
I was taught that if in the live moment of sparring or fighting, the oppoent closed the distance he eats the knee at closer range, if at mid range he eats the shin and at a slightly longer range he eats the instep/foot. This is simply how the round kick has been taught here in the states in Muay Thai & Bama Lethwei for nearly 40 yrs and it works.
Don't get me wrong, I am not saying my way is the only way, there are variations like the Stick Kick or Short Round that have their own dynamics and function, but for a traditional high round, this is what I believe in. Knee, Shin, Instep all from the same pivot.
While I understand differing camps of kickboxing teach slight variations on technique, when I have used the sound principle of pivot for the knee, shin kick & instep round motion is the same, I tend to hold to it and uphold it. I trust others will hold to their Kru or Sayas preference in these variations.
Some profess, pivot a full 180 degrees, some profess pivot a minimum of 135 degrees. Some profess kick up on an angle of near 45 degrees and some profess kick as near horizonal as possible as not to kank your shin/instep on an elbow guard/spike. These are all camp specific so do as you all choose.
I do agree 100% witht the poster who stated "The pivot alone can make or break you kicking prowess", that along with my instuctors insight, a good round knee makes a good round kick, I feel good knee mechanics make good kicking mechanics depending on your camp.
BTW alphacat, where is your Kru or coach when you have difficulties like this? Proper round kick mechanics specific to any camp is basic and drilled from like week 1. Muay Thai & Bama Lethwei bread & butter is Front Thrust (Teep) and Round Kick (Dtae wiang)
Best of luck developing the good skills you seek. Pay your respects to your Kru