A couple of pics of one area where it could be said the SPF is 'Simplified' or whatever, note the 'ribs' or 'formers' inside the sponsons, on the SPF they are notched on the flange & have a 'relief or cutaway' in each corner to make the parts easier to form. Probably doesnt remove much if any strength, but definitely makes each part easier to fabricate or form, have a really close look at some of the pic's of the 'original' cars or those from GOX-Jimmy Mac-Dave Brown & you will see several other areas where similar methods have been used. First pic is to 'original dwgs' -second is SPF.