I don't want to rain on your parade,but shocks and struts to not support the vehicle.That is the job of the springs.Shocks control the rebound of the wheel.Most coil springs fail due to constant overloading, excessive up and down movement or just a general breakdown due to metal fatigue. Springs can also corrode and rust. How do you know if you have a suspension problem? You'll probably feel it if a spring fails, your ride will become hard and jarring. Failed shocks may result in excessive "bouncing" or up and down movement of your car's front or back end. It may also become harder to steer, and could feel like your vehicle is pulling to the left or right.And as far as placing spacers between the coils,thats a no no.Automotive coil springs are wound tight at the top and bottom and loose in the center.Each part of the spring controls a certain type of force.The tighter windings controls normal road vibrations and the loosely wound control the heavy loads,like potholes and speed bumps.At 300lbs your probably collapsing the tighter windings.I would recommend replacing the front coils with one designed for your needs like from Pohl Spring Works.