Well, what the Vbox does is intercept the DiSEqC commands from the reciever and convert them into signals that will control a regular 36v actuator or motor like used a big dish. I believe Cascades actuator isn't like a regular actuator used on a BUD but is instead kinda like a cross between a linear actuator and one of the small DiSEqC motors in that it recieves DiSEqC commands and power form the coaxial cable just like those little motors do. Therefore I doubt the Vbox would be of use with it.
Anyway, one thing you could do that might perhaps help a bit is to always make sure your tuned to a horizontal transponder before moving the dish. This way the voltage on the line will be 18V which may help compensate for the voltage drop along the length of your cable. Other than trying to shorten your cable run that's about the only practical idea I have.