Slider hitches are not design/intended for hwy speeds in rearward position.
Rearward position is intended for slow speed Maneuvering
5th wheel pin weight is set up over the axle so rear axle 'carries' the weight
But it's your equipment ---no one is going to stop you from doing so
Might want to check with your sliding hitch mfg. about restrictions/limitations on rearward position usage.
360# pin weight :H
5000# 5vr........pin weight S/B closer to 1000# (20% of 5vr weight)
360# is only 7.3% which is LOW for even a bumper pull tongue weight
Where are you getting those numbers ??
5000#/trailer & 360#/pin weight