I'm hoping that taking lots of weight of the bike will help. Ideally this will reduce stress on the transmission enough to let it live with a moderately tuned 920.
Also, using an Alloy barrel should be a positive for heat dissipation.
I wonder if the problematic Alloy barrel 920s and possibly the cast iron 920s suffer from inadequate interference between liner and barrel.
Vincents require 6 thou interference between the liner and the alloy muff. Any less and hot spots show up in a hurry.
At 6 thou interfence the heat transfer is good, the bores last and last.
That's an 84 mm bore so I'm thinking of going 5 thou interference at 81 mm ( 920)
The individual Vincent cylinders completely out in the breeze do have a big cooling advantage over even an alloy Norton twin barrel.
With the ventilated cast iron the interfence fit can't be very much, even where there is metal.
Glen