I have been using home-made handstraps on my F2, FA for at almost ten years now, and recently made one for my FM as well. All three cameras are motorized, so the drive handles make them relatively easy to carry, but nevertheless, the handstraps give an added sense of security as well as allowing me to loosen my grip without fear that General Relativity will make mischief with a camera and lens.
The straps are simply Nylon ones that were pirated from our kids old school backpacks.
The aluminum baseplates for the F2 and FM's motors were machined for me by a Tool and Die Maker, while I made the plate for the FA's MD-15 from extruded aluminum bits and assembled with aircraft construction-grade epoxy.
The straps were sewn to the bases with 50(?) lb test braided nylon fishing line, and fastened with Velcro.
They're not as elegant as those very spiffy milk-fed Vacuna leather handstraps with the embossed Nikon logo across the back of the hand that B&H and Adorama sell for 80 bucks a pop, but they've never let me down.
