A guy I know has tried the 4 channel and the 6 channel and likes them for some of his rc sailboats. Note also the "DIY" conversion kit from Corona. Even a little cheaper, if you already have a transmitter to convert.
There are extensive threads devoted to these Flysky-cn.com radios: http://www.rcgroups.com/forums/showthread.php?t=967207 Here is a review: http://www.rcmodelreviews.com/hobbykingrc.shtml They sell under many different brands and are bundled with model aircraft and helicopters. Get the 6 channel as it is programmable and only dollars more. Or if you get it here, same price (+gst) and local: http://www.snhobbies.com/product_info.php?cPath=54&products_id=358 http://www.snhobbies.com/product_info.php?cPath=78&products_id=511 (xmtr only) They also have receivers on special - get several! http://www.snhobbies.com/product_info.php?cPath=55&products_id=619 (rcr only) There is also a compatible 3 channel receiver without satellite. They do not seem to offer it but is available from r2hobbies.com under Turborix brand. However the 6 channel can be run without its satellite and ok range for surface craft which makes it about 5gms with out case, if weight is an issue. All Flysky systems compatible with each other.
I purchased a 4 ch tx which comes with a 6 ch rx as standard . The whole system works great ,be careful of the pins on the rx , you can misalign connecting the servo if you're not wearing your glasses as was in my case , no damage done . there's a lot of info out there . Hobby King were great with packaging and shipping . will purchase more . Hope this helps , PS.. Go for mode two which has the ratchet on the L/H side , non self centering for sail control... James