Had my first try with my new 7424 today. Bought it from Coastal Tool with the 6" velcro plate and 6" counerweight kit. Seems to be fine up to about 5 to 5.5 speed. After that it does not speed up incrementally but just seems to "jump" to high speed, vibrates madly, and splatters product all over the place. Any suggestions about what to do about this?