Spitfire Mk.I strange behaviour

[Flanker35M]

S!

First of all this issue came up after had a talk with a friend. He had ran some tests on Spits and Bf109E's and noted something. I tested quickly on ATAG with Spitfire Mk.I and noted the same thing as my friend. Let me explain.

First I took off with a Spitfire Mk.I with 25% fuel and NO ammo, so the plane is light and should go fast. I flew level for some time at sea level to stabilize things and I got 250mph IAS with full throttle(6.25lbs) and pitch on coarse(pitch 2 in game).

Then I took same plane with guns loaded and 100% fuel. Again stabilized to level flight at sea level. What I got now was 265mph IAS! So the heavier Spitfire was faster than the empty one. In both cases plane was trimmed so everything was centered.

My friend said this applies to Spits at least, has not tested Hurricanes yet. He did a comparison with the Bf109E-4 and the difference was a mere 2-5km/h so there plane weight did not effect the slightest. I need to test and verify this too.

Comments? I smell a possible bug here which hampers performance for some reason.