Looking to add another Backpack Sprayer to the arsenal and have been considering the SP. Does anyone use them and if so, what are your thoughts? I am considering the SP0 which is a diaphragm although it claims to have the power of a piston (up to 150 psi). The unique aspects of this unit are it has an agitator which recirculates the solution when you pump the handle. This would allow better use of wettable and meltable powders. The downfall I see to this unit is there are more places for leakage over time. The SP2 is a piston and only has one connection to tank and claims psi up to 180. Both units seem to be well constructed compared to the Solos and others I have seen or used. My problem is...I can't find anyone local that carries them so I have to go by pictures in catalogs. Difference in price is minimal and really not a consideration.