Hi,

I would start with the 10x7 and try the 11x6 later. The differences will be subtle and require slight retuning of the high speed needle. The 10x6 will give you better ground clearance for the inevitable heavier landings as you become comfortable with the modle. When the carby is properly tuned neither prop will "over prop" or risk damage to your motor, a "lean run" will risk damage. Always err on the side of a little rich.

Cheers,

Colin