I don't know if there is a definitive distance for the fully extended damper of any manufacture to conform to. If it is 227.5 mm, the variables that affect that are top mount positions & bottom mount positions. Fork links are often remade or modified to take a damper. Your's look to be remade
To make up any shortfall, the tops can be extended, but an alternative solution might be to manufacture custom bottom mound. Stainless for the strength would be good, but aircraft spec alloy would also work. Roughly speaking, it's depth would need to match the distance of the spacer portion of a standard screw in mount. It's width could be anything upwards of the 11 mm AF hexagon of a bottom mount, though matching the boss of the fork link would be better aesthetically.
Length (in the almost vertical plane) would be to suit. It would require two holes @ a distance your dampers are short plus a bit more for rebound.
The two holes would be M7 clearance to fit the fork link hole & M6 for the bottom damper hole. The M7 clearance hole would need countersinking or a counter bore, or the depth of this custom mount would be spot faced back, or machined back if necessary for the M7 fastener to clear the actual damper..
I think with a little bit of shaping, such a bracket would not look too 'gash' & would be hardly noticeable.