The frame 1 wherein said parallelogram shaped structure includes {TAIL ~ a pair} of retaining cables having an even, predetermined length and extending one along {HEAD ~ each} of the front and rear of the frame, from said axis to a diagonally opposite point of the parallelogram shaped structure 
The frame 1 wherein said parallelogram shaped structure includes { TAIL ~ a pair } of retaining cables having an even , predetermined length and extending one along { HEAD ~ each } of the front and rear of the frame , from said axis to a diagonally opposite point of the parallelogram shaped structure
OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH