If the instrument panel curve is correct,the coaming cutout is correct to the Spitfire engineered book and the distance between the canopy rails is about 22″ wide your fine..Problem with caste repros is that they are something like 5th generation copies where each generation shrinks a bit due to the casting process..Best is to make a new master pattern (off memory 11% bigger due to shrinkage) and get new ones cast..