The 262 carries approx. 3,200 lbs of fuel. Take one up offline set fuel burn to 0.001 and see how much of a difference there is in top speed with 100% and 25% fuel. You'll notice that the difference in top speed at SL is no more than 1-2 mph, and that's with a weight difference of approx. 2,400 lbs. You seem well versed in aerodynamic nomenclature, so I'm sure you know that induced drag only represents a minute part of total drag at such high speeds. A 4% reduction in weight would not affect top speed of the 262 in any measurable way; at least not with 1940s instruments.