I am frankly not a fan of high break falls. Step outside and do a high break fall on the pavement. Besides the obvious results of such an adventure, the high break fall keeps me from staying connected to the nage so that I can continue my attack.
I teach students proper ukemi. Maintain a connection with the nage, Conform and dissipate the force so as to first, learn to change levels safely; secondly neutralize the incoming force; finally, return the force - all while maintaining your center and structure. If you are doing these things correctly and you are thrown in such a manner that you really do have to do a high fall, your body will conform to the forces so that you do not get injured.
Launching yourself into the air breaks the ki flow, which tends to increase the risk of injuries when being tossed on hard surfaces. I have done sacrifice throws and have been tossed on hard wood floors and pavement without bruises or injuries because of the above-mentioned factors. Not many people want to try practicing that way very often; I wonder why?