I just spent an hour scouring the net. Jeez, it's hard to find enough info on Formidable and Indomitable! Initially (from most references) it looked like the two carriers had mostly Martlets, but I kept digging and found that it seems like, during the Operation Husky timeframe, Formidable had mostly Martlets and Indomitable had mostly Seafires.
I'll ask Newman (the scenario designer for this one) if he wants to have the RN contingent split up into two forces.