Am wanting to get a machine for home use, mainly on my own racquets. Because I'll have to store it in a closet when not in use, am concerned about the weight and "portability" of these. "Nothing But Tennis" told me the Revo 4000 is 78 lbs - seems pretty heavy. That's more machine than I'd probably get, but it got me wondering how heavy the simpler machines were. Examples are Alpha DC, Klippermate, Silent Partner. Any info and experience will be greatly appreciated!