I've got some photos somewhere of the shoulder strap anchor points, but no doubt somebody will reply sooner!
Bear in mind that, generally, all harness straps were left at extension, slack, in order to ease fastening, and then pulled tight once fastened. In most cases, in all Air Forces, straps were (and still are) arranged in such a way as to facilitate entry into the seat, and easy donning of the straps. Exact positioning depends on aircraft type of course, and may have the shoulder straps spread either side of the seat, or over the seat back, for example, or hanging over the cockpit sill, with lap straps out of the way (of the seat pan), perhaps hanging down from their anchor points.
Of course, this partly defeats the object of including the harness on a model, as it might not be seen !!