Old, old trick for managing long tele's like this.
A couple of
DIY ones from Pop Mechanics
I can't find it right now, but I also saw an article in an issue from the 40's or 50's that used a real gunstock from a 22 rifle.
I'm tempted to build one for myself; I have a itty-bitty Pentax Q10 DLSR that I have an adapter for my old screw-mount 35MM lenses; a 135mm telephoto ends up being the equivalent of about a 750mm lens; an F2.2 750 mm-equivalent telephoto is quite a good lens; but is damned near impossible to use hand-held, and if I stick my bigger zoom lens on it it IS impossible to hand-hold.
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