Thanks for the hints, guys. I'm determined to do this right - that means having a real standing rest with proper support for the forward hand, and, preferably, some support for the right elbow, as well as adjustment for height and angle - something like what is pictured in an illustration in W. W. Greener's book. I'll come up with something soon.
I've seen the effects from firing highpowered rifles over the tops of cars, so wouldn't try it myself. I've got Stoney Point rests available, but feel they are not sufficiently stable for serious work when you have so many variables in a new rifle and untried ammunition combinations, not to mention a horror of inadvertently shooting the bejeebers out of my poor old chronograph (again).
500: This side of the world, 'bonnet' is a style of lady's headgear - but due to my facility with dialects, I know you meant 'hood'. :-)
mhb - Mike