I wonder if we could get over the incapacity problem by having positional lanes with four targets, two standers and two kneelers. They would be paired, one stander and one kneeler, and you have the option of shooting either, but not both. The stander would be there for anyone who can't kneel, or chooses to take the stander instead of the kneeler. As standers are just about universally considered harder than kneelers, the stander would be at a closer distance, say 75% for example.
So the kneeler might be at 40 yards, and you can take a 30 yard stander instead.
Does that seem fair? Should the stander be even closer?