Interesting concept. Horsepower loss from weight. I don't recall weight being a factor in calculating horsepower. It may require more hp to accelerate a given mass at the same rate if the mass increases, but there is no hp "loss."
Horsepower is simply the ability to do work. The simple test says, if I make more horsepower my top speed is higher. If I reduce the weight of my car does top speed change? No. If I make more horsepower does top speed increase? Yes.
If I reduce weight does the rate of acceleration change? Yes. That's what this is all about, not horsepower loss.