The backseat gets a little less G than the front- up to 1/2 g I recall reading for the F4 (back seat is closer to the C of G, think of levers and rotational velocity etc.). What really screws up the backseaters day is when sudden applications of G are unadvertised and Baldrick finds himself with his head in his lap and suddenly able to accomplish something he probably spent most of puberty trying to do with little success (if the harness wasn't in the way

).
For the record, the mighty Phantom was the dream aircraft for me growing up. It just looked the part- mean as a bag of mean things. Too bad it was in the process of being retired as I arrived.