I too like the 8500c with Cyclic Hotline and Helieng , but........as I said earlier if your doing a 407 or a 412 you need the RADS , I can give about 3 examples on a 412 and 2 on a 407 in the last 2 years were the 8500 couldn't get the a/c in limits we had to fit the RADS kit and it came in, this is a case of buy the equip the manufacturer recomends not somthing else.
We use the 8500c's on 206,206L, 212, 365's ,S76's and Super Pumas (when Hums fails) and it works great and we have a RADS kit just for 407 and 412 use which was bought just for the Bells because of past problems.