I don't think Dynastar speed is too long for your size, it is just that they are not a bump ski. It is a cruising ski.
In fact, as a pure bump ski goes, the length (~185 cm) would probably be just right.
I just bought a pair of K2 Outlaws, a pure bump ski. 180's. The shovel is a bit stiff as mogul skis go, but compared to my Scream Hots (175 cm), its noodley. You must remember that mogul skis are much narrower than tosays "shaped ski". They are more traditional. They are not good for much outside of the bumps. Even some of the "hybrids" like the Rossi Scratch, which have a bit more of a sidecut to em are not freat out of the bumps.
So I plunked down $140 and got myself a ski that is just for bump days.
I bought them here:http://search.stores.ebay.com/search/search.dll?query=mogul&srchdesc=y&sid=30214299&sto re=Denver+Wholesale+Skis&colorid=0&fp=0&st=1