John, the only reason I can think of where 2.4GHz solved the problem for Tilly was that the 40MHz system was failing due to interference. Installing 2.4Ghx didn't solve the problem, just masked it and possibly left the interference to interfer with others. Why do you think the 2.4GHz solved the Tilly problems?

Of course 40MHz systems are still for sell and I have a number of customers who will not touch 2.4GHz. However, in general the sales are on a decline.

Also, a real issue with 2.4GHz is that they are biased towards aircraft with in general just a single failsafe channel. This leaves the other channels often staying put after loss of signal etc.. You don't get this problem with 40MHz.