English w-ind tunnel tests were conducted with three different diameter smooth, blunt nosed bodies behind a two bladed propeller having a pitch/diameter ratio of 0.7. The three body diameters were 0.40, 0.60, and 0.75 times the propeller diameter. Propulsive efficiency with the smallest diameter body was only two percent less than that of the propeller alone. Propeller efficiency was reduced by about five percent with the medium sized body, and about seven percent with the largest body. Thrust loss would be about the same as efficiency loss.

The fuselage that you mention is a highly unusual 81 percent of the propeller diameter. No tests were recorded with such a large diameter body, but I would expect thrust loss to be in the order of ten percent, if the body behind the propeller is smoothly curved.