There was a really good picture sequence of what Tomba was doing in a ski magazine years ago.
Basically as he entered into a turn his feet were back and as he came through the turn to just before the transition he kicked his feet forward, At the start of the transition and during the transition it was a reload (bring the feet back) and repeat.
It took me a little while to get this on both my GS and SL skis, but I found once mastered, this was a great way to accelerate and pull away from friends while skiing .
Downside was if you messed up on the timing at all everything got messed up at the same time.
If memory serves correctly this was published towards the end of his skiing career.
On onto shaped skis, I find that the motion on the shaped already replicates this technique just not to the extreme that was required on the straights. I believe this has more to do about the edge angles that we can achieve on the shaped skis vs what was possible on the straights. Pushing the limits as we did on straights onto the shaped will likely increase the chance of injury (ACL) as the body position along with the edge angles and the fact that the feet are ahead of the COM/COF set one up for potential phantom foot.
Don't get me wrong, I'm glad I know how to do it, I just don't see the need on shaped skis if they are skied as intended (at least on groomed/hardpack/ice)
I would honestly love to hear what you have to comment on this Bob Barnes as you likely have both more experience on both the straights and shaped then I can ever achieve.