Actual gound level test has resulted in 0.7 miles before serious glitching. See:

[link=http://www.flyingcirkus.com/forum/Flew_and_Biff-_tested_JR_Spread_Spectrum/m_96209/tm.htm]Crikus Report[/link]

This is at 1/10th watt. FCC allows these 2.4 GHz units to transmit one watt. Note that a full flying field was the back ground for the test.

About the sequency: You can have the same "code" as another flyer as long as your timing is different than his. Even if you accidentally hit the same minor frequency (sequence) the redundancy of the data stream (CRC checks and such) will just throw that part out. Since that "part" is one thousandths of a second (or less) you will see no impact on your eye-hand closed loop control. the high end miltary stuff uses adaptive logic. If there is a big broad band frequency spike in the middle of the spectrum being used, the adaptive logic shifts to the outer bands. Also if there are too many hits during the sequency the adaptive logic changes the sequency or even goes to random shifting.

As to wither your flying field will allow these is really the meat of the argument. No reason not to as per the manufacturers suggested use. Actually would be safer for all flyers.