The weights are correct. A Spitfire XVIe with tips removed is 7241 lbs loaded compared to a Spitfire F. IXc at 7303 lbs loaded.
The Merlin 61 is a +15 lb engine. 1560 hp at max wep.
The Merlin 266 is +18 lb engine. 1720 hp at max wep.
Wing areas are 242 sq ft (IX) to 231 sq ft (XVI clipped).
So the XVI has a wing loading of 31.35 ft/lbs and the Spit IX has a wing loading of 30.18 ft/lbs.
Very slight advantage to the IX (around 3 percent) in pure wing loading only.
...But the IX would only out turn a XVI clipped if they had the same engine, which they dont. The XVI is faster, has less drag, and climbs better as a result of its better power-weight ratio. What made the VIII and XVI what they were the more powerfull 266/66 engines, optimised for low-med alt flying.
Just to compare, a Spitfire XVIe with a full span wing weighs 7450 lbs loaded and a wing of 242 sq ft, giving it a wing loading of 30.79 ft/lbs, but with the Merlin 66, it also should out turn a IX, or a XVI clipped (just by a very small bit).
Also, the clipped tips on the XVI dont have much of a detriment at sea level alt, where almost all MA fighting is done.
The Spitfire VIII is a heavier bird than either at 7808 lbs (it has more fuel), but is close to performance, because it has full span wings and a Merlin 66.
So in a arena matchup, mutch will depend on the fuel states of the IX, XVI or VIII as far as a sustained turn contest, and relative energy states at the star of the fight, and of course, pilot skill. Anecdotal comments from players will be widely different, because of the many variables in those fights: weight, energy, pilot skill, position, ect.
