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.
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 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 
re****ted capacity of the flat free tires.
Any suggestions?