Flat free ground handling wheels

I recently tried a pair of Marathon flat free wheelbarrow tires to replace
my pneumatic tires that had developed the habit of slowly leaking out the
air.
@#$%^ The rolling resistance was so great I couldn't move the helicopter by
myself. In fact even with my wife's help it was very hard to get the
helicopter moved on concrete with the flat free tires. Looking at the
contact patch, there was approximately a 3" long contact area. Replacing
the flat free with the pneumatics, I was again able to relatively easily
move the helicopter. Weight of the helicopter was slightly less than the
reported capacity of the flat free tires.
Any suggestions?