403 Hand brake adjustment

[peterg]

The brake is slipping on steeper inclines.
Bristol said not to adjust it on the cable, so I did! to no effect. They also said to adjust it on the brake shoes, but it is correctly adjusted.
So what is the problem?
Checking under the car the central arm fouls the off side brake rod when pulled.
I intend de adjusting the cable to put the arm back as far as possible and presumably shortening the brake rods so that the rear brakes are activated earlier and before the arm hits the brake rod.
The question is how do I adjust them and by how much?
The outer ends are threaded, no sure about the inner, by the operating arm, which is harder to reach.
Advice on the adjustment and how many 'clicks' to get the brake fully on would be appreciated. Before being played with the lever went the full distance, currently it pulls half way up.
Also, the cable curles around the exhaust? It there any was to protect the outer cable from the heat?