The bigger tail surfaces would help a bit with the balancing. Maybe put the radiators in (inside?) the tail too. I believe some of the long Griffon Spitfires needed extra weight in the tail to balance.
Actually all the Spitfires had some sort of ballast perttime, there was a special frame built into the end of the fuselage, right where the tail assemble was bolted on. Depending on what motor/propeller combination was installed depended on how much ballast was bolted in. This ballast comprised of steel plates of various thicknesses, stack on top of each other and had a big bolt running through the lot. They had to go this way because all through the Spitfires production, from the Mk.I to the Mk.24 (including Seafires, Spitefuls & Seafangs), the fuselage length (that's the distance from the engine bulkhead to the tail assemble joint and even to the rudder hinge line) never changed. Now I'm not saying the
overall lengths didn't change, just the fuselage length.
One of my up coming project is to build a Spitfire with a Mustang style radiator duct, apparently Supermarine studied all the various radiator styles at one time ot other.
This one below for instance has wing leading edge radiators but I have also stretched the rear fuselage by a scaled 24" [610mm) which is about 8.5mm in 1/72, I'm going to do a regular Spitfire the same too.