I'm a bit baffled, a 90hp Supercub with more than 200m of runway is going to do a lot of taxiing. From checking, the shortest runway at Sibson is approximately 500m, which should allow a take off and landing. Unless you are training at another field.
Cub brakes are usually not bad, so you might get two 'good' applications which would kill the speed before they start to fade (unless they have been swopped to discs) but on grass I would not expect to use them at all. If you need the brakes for anything other than a stiff crosswind then something is not right by quite a margin.