Thin wall molding is a relative term that implies the flow length is long with respect to the part thickness and material viscosity…
Our thick PVC parts require a higher packing pressure than the injection pressure, yet the training states this is typically the case for thin-wall molding. In our case, the parts are often over 0.300″ thick… can you please explain this?
In your case, the walls are thin relative to the flow length for the very high polymer viscosity of rigid PVC. I recommend running a rheology curve (or at least a speed study), take a picture of the shorts and take notes at each speed (ie gate appearance, part appearance, burning, etc.). With PVC (& CPVC), the viscosity is very high, but the polymer is also very sensitive to shear thinning which allows for some reduction.