thauma wrote:[...] personally I find the kick-back very effective, and found it worked well / better in competition [...]
Were these judo competitions where the back-kick version worked for you? If not, what sort of comp was it? If so, what level of competition are we talking?
I can't say I've ever seen the back-kick version in judo. It's always struck me as a misinterpretation of the principles of the throw. (Surely, it is hard to pull uke forward whilst you enter and back-kick? I.e. I'd expect the motion of a back-kick to puch uke backwards rather than pull him forwards.) But, I'd loved to be proved wrong.
Also, I'm not sure the throw can be described as "perpendicular". The instructors I've met who use harai seem to draw uke at about a 50 - 75 degree angle rather than 90. (If you were to draw a straight line intersecting uke's feet.)
Disclaimer: Harai-goshi isn't really my throw.