RE: Helimotor for plane
I'd bet that it would work fine, making it a very light plane.
I purchased a Lancair EP from Tower a few years ago. It came with a geared system and a brushed motor and a 1800mAh NiCD battery pack...
I replaced the included motor with a rather tiny Ultrafly 3200KV Outrunner "B" series motor.
The weight savings was amazing, and the power available transformed the plane completely.
The only thing I had to do was change out the motor ( the Ultrafly was a drop-in fit! ), and ESC, then use my existing 2200mA 11.1v LiPo packs.
When I show the components to other EP flyers I often get amazement at the realized performance with such a small motor.
The motor sees very little load due to the gearing.
The geared system has held up well so far. It's too bad they are often so overlooked.