In general, is it possible to bind a Tx to a heli with fewer channels? I've moved on to 4ch FP but have some 3.5CH toys that work nicely.

In general, no two brands will cross-bind.

I fly my 4 channel V911's with a FS-CT6B 6 channel transmitter.

Turnigy 9x - 8 channel transmitter will also fly the 4 channel V911 helicopter.

I fly my SP328, a 4 channel helicopter with the J6, a 6 channel transmitter.

A DX6i, a 6 channel transmitter will fly the Spektrum brand helicopters, even 4 channel helicopters like the 120SR.

Generally, the number of channels transmitter to helicopter will not stop the radio system from working.

But no, in general, different brands will not bind, though not because of the number of channels.

And binding is not flying. Some radios will bind, but not fly.

Ok. Thanks.

Ribble, So what you're saying is that the v911 heli won't bind with a Spektrum transmitter?

In general you can bind to a lower channel aircraft.The only thing you need to know is that most 3 - 3.5 channel aircrafts have what is called a 4 in 1 receivier and has its only wavelenght that it is only used with the stock controller.
Now you can take out the 4 in 1 receiver and put in your receiver but will have to mode in in a few ways