A cooperating rack structure comprising at least two modules (100/100'), wherein each module (100/100') comprises: a cylindrical composite fuel tank with a first end and a second end supporting a valve ; a first sub-rack cradle disposed at the first end; a second sub-rack cradle disposed at the second end; wherein each sub-rack cradle comprises a substantially vertical first outer wall , a substantially horizontal second outer wall , an arc shaped inner wall having a top arc end and a bottom arc end , a structural body frame member affixed to the first and second outer walls and the arc shaped inner wall, a first tensioner guide adjacent to the top arc shaped end , a second tensioner guide adjacent to the bottom arc end , a catch formed in each of the tensioner guides, a top bracket mount extending from the first outer wall, a bottom bracket mount formed on the second outer wall, a front rack leg mounting plate formed perpendicular to the second outer wall , and one or more back rack leg mountings formed along the first outer wall ; one or more tensioner assemblies ; and two straps , each strap attached to each of the first and second sub-rack cradles and wrapping around the cylindrical body of the fuel tank , each strap having a first strap end and a second strap end with a strap mount guide formed in each end, wherein each strap is affixed to the sub-rack cradle via one or more of the tensioner assemblies , with the tensioner assembly having a bolt with a head , a plate , a spring and a nut used to compress the spring against the plate; and wherein the at least two modules are mounted together in a vertically stacked arrangement, with each successive upper module above the prior lower module being affixed via top bracket mount of the lower module to bottom bracket mount of the upper module forming a connection , and wherein the mounting places the substantially horizontal outer walls of the sub-rack cradles of the upper module above and not touching the fuel tank and straps of the lower module . a cylindrical composite fuel tank with a first end and a second end supporting a valve ; a first sub-rack cradle disposed at the first end; a second sub-rack cradle disposed at the second end; wherein each sub-rack cradle comprises a substantially vertical first outer wall , a substantially horizontal second outer wall , an arc shaped inner wall having a top arc end and a bottom arc end , a structural body frame member affixed to the first and second outer walls and the arc shaped inner wall, a first tensioner guide adjacent to the top arc shaped end , a second tensioner guide adjacent to the bottom arc end , a catch formed in each of the tensioner guides, a top bracket mount extending from the first outer wall, a bottom bracket mount formed on the second outer wall, a front rack leg mounting plate formed perpendicular to the second outer wall , and one or more back rack leg mountings formed along the first outer wall ; one or more tensioner assemblies ; and two straps , each strap attached to each of the first and second sub-rack cradles and wrapping around the cylindrical body of the fuel tank , each strap having a first strap end and a second strap end with a strap mount guide formed in each end, wherein each strap is affixed to the sub-rack cradle via one or more of the tensioner assemblies , with the tensioner assembly having a bolt with a head , a plate , a spring and a nut used to compress the spring against the plate; and <EOS>