You do pay a penalty in the form of extra stress as the props rotate through the wing wake. The flight handbook has graphs of the forbidden ranges of airspeed and rpm. (AN 01-5EUG-1, "Flight Handbook USAF Series B-36H Aircraft," 1953)
I may have given the impression that prohibited speed and rpm combinations were something unique to pushers. Not at all. "The possibility that flight and ground operation might take place at engine and aircraft conditions where flexural propeller vibration stress levels exceed allowable limits has resulted in operating restrictions." (1C-124A -1, C-124 flight manual). For instance, 1250 - 1850 rpm was prohibited on the ground except to quickly pass through that range. In flight there were additional restrictions that depended on weight and speed.
The B-36 flight handbook says, "These limitations are primarily based on propeller vibration limits but the vibrations may be of such nature that they can also weaken the propeller shaft. The vibratory forces are caused by power impulses imposed as each cylinder fires; by the aerodynamic disturbances created as a blade or blades pass through a region of turbulent air behind the wing or adjacent to the fuselage; and by other causes such as misfiring cylinders, malfunctioning vibration dampeners, and extended flaps."
Both the B-36 and C-124 used Curtiss 3-blade propellers.
Earlier I mentioned the B-36 propellers were parallel to the wing trailing edge, which was swept back 3 degrees.. This was a factor when you feathered a propeller. "On this airplane the engine nacelles are not parallel with the fuselage center line in the horizontal plane. The nacelles are 'toed in' at the propeller end, resulting in the propellers on one wing having a slightly different relative wind than those on the other wing. This condition may lead to propellers on engines No. 1, 2, and 3 windmilling in a direction opposite to normal operation when they are feathered."
That slow reverse windmilling will eventually damage an engine due to inadequate lubrication., so the engineer (coached by a gunner in the rear compartment) would jiggle the manual pitch switch to stop the rotation.
Finally, a bit of B-36 trivia. It's well known the plane entered service as a 6-engine bomber, and the jet pods were added later. What is not well known is that the pods were removable! "Occasionally, it may be desirable to operate the airplane without the pods installed to obtain maximum range (with a sacrifice in possible top speed)." Pod removal reduced the B-36H operating weight (crew + crew equipment + ammo + unusable fuel + other fluids fully serviced) from 181.800 to 167.600 lb, or a 14,200 lb loss. Max weights were 357,000 and 330,000 respectively. I have never seen a photo of a de-podded B-36. It must have happened rarely, if at all.
Those max weights are from the flight handbook charts, but the same charts show the B-36H can fly with an massive overload if you accept the risk. With one jet pod (or any two piston engines) inoperative, the weight necessary to bring service ceiling down to sea level is more than 550,000 lb.