I did ask kancho to show me how to do the technique correctly last year. I told him my sensei experienced the same technique from kancho some decades back and I wanted to experience the same.
My sensei said when Kancho did it to him, he flipped over on the same spot without feeling any pain. He did this several times. And in no way was it a joint lock throw he emphasised.
When kancho did it to me though, he basically utilised enshin from the forearm all the way until my shoulder and the fulcrum is that shoulder not the elbow lock, thus when being thrown imagine yonkyo...
In the end I didn't fall in the same spot and I did feel all of the technique. He must have let me off since I probably don't have the ukemi skills of sensei.
Anyway, the fact that you want to post with your lead foot is irrelevant when your face is going to be planted on the mat. That being said, if the fulcrum is still the elbow, yes your are likely to be able to stop it. I wouldn't but you could.
Alberto: Yeap I'm not saying they are sterling examples of Aikido but I found it difficult to find any high levels demonstrating this technique but I may have struck gold:
Watch this one where Gozo Shioda does it and I don't see any use of the leg trip/position. That being said it does look like the uke is flinging himself (though with someone as bad-ass as Shioda one can hardly blame the uke).
But what is more telling is that udekimenage is known as 'hijiate' in Yoshinkan which if I understand correctly is translated as 'strike to elbow?' If so we can safely conclude that this technique as originally designed was to break/strike the extended elbow rather than throw itself and that the dojo version of this technique is just for safety rather than it being an effective technique in its dojo form.
These techniques really should come with an instruction manual :/
Appreciate anyone in the Yoshinkan school to comment on this also