Well, I don't think I'd try the as-tight-humanly-possible approach Berger is suggesting. After all, people and spanners come in different sizes (which will sound very stupid to Berger if he is 6'6", 280 lb.). While we A7/A10 owners don't have the benefit of BSA-published torque specs, they did start publishing them for the A50/A65 models. For cylinder base studs (from that list), 18-20 ft.-lb. If that feels untight when reaching the top, one could probably add a couple of pounds if it seems comfortable.
Now, unless you own a special torque wrench that accepts Whitworth spanners, you will need a way to apply the torque with your 1/4W open end. I do this by pulling on the box end of my box/open-end spanner with a fish scale, stopping when I reach the value I've calculated based on the length of the spanner. I will usually calibrate the fish scale before doing this.
Richard L.