Way back when...
When the 8700g was released to John Q. Public, there was no sticker on the case. After many people complained about the glitching when using PPM, JR looked into it and promptly resolved the issue by applying the PCM USE ONLY sticker. You can however use the servo in PPM mode IF it is directly plugged into the reciever and not down-line from a gyro.
It is a great servo, super precise and fast. You must remove all forms of binding and/or resistance in your tail linkage or it will fry in short order. Also, I would not reccommend running it with a boom mount and unsupported carbon rod for a couple reasons.
1) Boom mounting (or rear mounting on an aftermarket plate) places the servo in an environment of MUCH higher vibration than the stock forward mounting. The MA rear mount kit for the Xcell is a little better with the damper rubbers but IMO is still a higher vibe environment than up front.
2) An unsupported carbon pushrod, although free of any resistance, is not free of resonance and vibration. These vibes will wear out the servo MUCH faster than a supported linkage. MA has a nice pushrod kit with supports that minimize the resonance but can be just as much a P.I.T.A. to set up smooth as a stock linkage wire.
3) It's a dirty environment back there with the exhaust flowing everywhere.
4) In many instances, a servo extension must be used to connect the servo to the amp. I like the K.I.S.S. method and believe that the more connections you have, the more chances of failure you have.
I used to throw a rear servo on everything I owned. I noticed that I was experiencing servo failures and excessive gear wear. When I would change the gears on my Futaba 9203 and 9205 servos (@$60 a pop) I would find them dirty and oily inside. I have yet to have a tr servo failure or have had to replace the gears on a forward mounted tr servo.
Also, Panos and I spoke with CY last year at Toledo. Panos asked why he (CY) was not running a boom ounted servo and CY's reply was close to what I just mentioned above. Very sound advice from someone who has forgotten more about helicopters than most of us will ever learn.