Im running Spuhr SP-4802 34mm, 1.5" 44.4 MOA cant with a Vortex HD G2 4.5-27x56 with AAD Mount caps, and I have about a hundredth of an inch of clearance, and about 3 hundredths of clearance with the sunshade and no caps, Im not able to run caps with the sunshade. Most 56mm objectives require a 1.5" mount anyways. With a 50mm or smaller objective, youll be able to drop the mounts a little bit lower.
However, if your neck is hurting while in the prone, you need to adjust your position, lower or raise the bipods (most likely raise), straighten out (spine parallel with the axis of the bore), dont torque your neck on to the cheek rest, dont scrunch your shoulders, etc.