Dick,

I hate to keep beating this subject, and I respect your experience.
Maybe this will help...

Power = Power
Watts = Power
Total Thrust = Power
15 pound airplane hovering = 15 pounds of thrust.
Watts does not equal torque.
Propellor torque creates torque roll.

Torque required to spin a propellor to hold a 15 pound plane steady varies with the diameter, pitch, and blade configuration, (narrow blade, standard blade, wide blade, and 2 blades, 3 blades, etc.).
Different propellors require different torques to perform the same amount of work, just like different wings produce different amounts of drag to produce the same amount of lift.

Would you agree that you can liken the prop blade to a rotating wing?
OK, with a larger wing area, you do not need to produce as much lift per square inch to have the same lifting effect overall, right?
Example:
If you have 10 pounds of lift using 700 square inches, there is a larger pressure differential between the top and bottom of the wing than 10 pounds of lift using 1000 square inches.
The same applies to a propellor. A larger diameter propellor does not have to produce as much thrust per square inch as a smaller propellor to achieve the same overall thrust.
Make sense?

Powerlines,
The 18x4W may increase your torque roll because of WIDE blade has more rotational drag than the standard blade.
Try a 18x4, not 18x4W.

Bob