Did you mean 4-point Dave? .... if your belt slides off your shoulder you sound to have 3-point already? ..... my car came with 4-point as it was used for hillclimbs ... they certainly hold you in place ... the only downside is I've never seen a 4-point inertia-reel belt so you sit where you sit .... fortunately all the switches etc in a Morgan are close to hand.
K