Duplanits was a big time speed demon! And one of my favorite jumpers, along with Hufman and some other little guys. There is no way to jump that high without bringin' some serious heat into the box, no matter what size the jumper is. Those two guys were little, and made up for it in velocity.
Just as a side bar to this discussion for everyone out there, there is much more to being fast in the polevault than just moving fast. There is also serious concerns about balance and power. Just moving fast dosen't guarantee that energy will be transfered. I don't know if there is a technical name for it, I call it effective speed, and I am sure everyone knows what I am talking about. There are guys who have raw speed, that simply isn't effective, and others who have very little speed, but a high degree of effective speed. Then there are the dangerous fiew, like Bubka, who had both.