Ah, the trials of finding a 500/600/700 series motor to match a sedate scale model. I've been caught out a few times with an advertisement or even the sellers personal assurance that a motor would be an ideal match this type of model. Perhaps the worst example was a kit based on a canal boat, the ultimate in sedate scale models?, which included a motor that would have been at more at home in a screaming fast electric model. When tackled about this, the kit manufacturer admitted he had never actually tested the motor the model, but had been assured by the motor supplier that it would be perfect for this model...!!!
For this reason I tend to use the "Rock Climber" types of motor, which have many more armature turns, hence lower RPM but lots of Torque, to directly drive surprisingly large propellers safely. I've even rewound stock 27 turn motors (which were well past their high performance days) with something like 100 turns to carry on sailing in scale models.
There is an alternative of using a lower voltage battery to tame the speed of a motor. I've used a 2 Volt battery (usually used to start glo-motors) to power a scale model using a stock 540 motor. If using an ESC you simply have to connect the 2 Volt battery to the ESC but keep the BEC switched OFF and power the Receiver with a separate battery.
Glynn Guest