set and varied to employ mutual facing or mating integral tension half struts 20 b 1 and 20 b 2 all other construction and assembly methods remain the same or similar fig1 d is a section view of said right rear wheel support structure 6 of the present invention looking forward that illustrates another further variation or modification of fig1 a to be utilized preferably with main frame structure schema of fig1 a wherein said outer shell half 31 c is a continuation of said outer shell half 31 of said airfoil down tube 3 and wherein said integral tension upper and lower struts and interior integral tension strut configurations of fig1 b and 16c are replaced with two sets of dual parallel and lineally running mutually facing or mating integral tension struts 20 c 1 and 20 c 2 and wherein shell moldings 35 and 16 are varied slightly to 31 c and 16 c and share the same common central plane of assembly as do said dual integral tension struts 20 c 1 and 20 c 2 and utilize seam overlays 47 c and 48 c over their common seams all other construction and assembly methods remain the same or similar fig1 is a side interior view of said main frame structure 1 of the present invention illustrating an alternative arrangement of struts and ribs and an alternative method of assembly along a central common vertical plane wherein said top back and bottom caps 28 29 30 of fig1 or the preferred method are integrated into the left and fight outer shell moldings 43 and 44 and upper and lower integral tension struts 24 25 and 26 of fig1 or the preferred method are replaced with two dual mutual facing.