That is so, but even with the single stage charger, Pratt's altitude performance was better.
Cheers,
Wes
The 1942-44 vintage R-2800 was making 100 rpm more, and had 200 cu in more, so yes, it is normal to have more HP all-around. Above 13500 ft, some 15% more - at 15000 ft, it was ~1550 HP for the R-2800 and ~1310 for the R-2600; all for 1-stage engines, military power.