I would hazard it's already a foregone conclusion that you'll enjoy your 8FG Super and you'll be glad that you spent the extra $$. It's jam-packed with nice, easily programmable features and also guarantees you the satisfaction of reliability and built like a tank. It's also future-proof - able to handle any possible new-fangled gizmos that may come along later on down the road. The only downside is the rather steep cost of extra receivers. Fortunately there are available receivers now which are 100% compatible with the Futaba FASST system at just a fraction of the price of dedicated Fut' receivers. And in case you're wondering, yes - I use them myself, and yes, they are 110% reliable - totally glitch free.
With regards to your last question, all I can say is that I've been using Spektrum digital servos in a model airframe in conjuction with my Fut' transmitter for some time now and have not noticed any compatibility issues at all - they work just fine. But it might be worth mentioning that most all digi' servos tend to draw more current than their analogue counterparts. They are also prone to 'hunt' for their neutral position when the transmitter stick is at its centre position. In effect, the servo horn tends to constantly twitch, which in turn means even more of a drain on the receiver battery. In my case I use a 5-cell battery pack to supply the receiver and I've never experienced that unwanted 'hunting' effect; the servos remain rock steady regardless of the position of the Tx stick. I can only assume that the reason some folk are experiencing twitchy digital servos is maybe because they are using a 4-cell battery pack. Who knows, I'm just guessing.
Also, digital servos do operate slightly faster than analogue servos, which is why the flyboys who operate super-fast 3D airframes need a fast response on their ailerons and such. But the way I see it, digi' servos are maybe an overkill when used for model boats. In my humble experience, bog-standard Futaba analogue servos are sufficient for 99.9% of the time anyway. On the other hand, since you already have several digital servos to play with, then go ahead and try them by all means. If you're using them in a super-fast boat you might appreciate the slightly faster response to the rudder input from the Tx. If you should notice any unwanted twitching, then you might try using a 5-cell battery to see if that cures the problem.
Now, are you sitting down? Sitting comfortably?......
All that you have read above regarding digital servos is just my way of trying to sound polite and unbiased. If I had the chance to say what I really think of digi' servos I'm sure I'd be shot down in flames. Basically, I think digi's are more trouble than they are actually worth. They are waaaay overpriced and waaaay too power hungry. The only reason I installed them in my airframe is because they were all I had to hand at the time. As I said above, I use a 5-cell pack, rated at 2900mA. 2.9 Amps should theoretically last for ages before needing a recharge, but a digi' servo on each aileron, and another on the throttle and one more on the rudder means that my 2.9A battery needs a recharge after just a measly thirty minutes or so. Yes, I am biased towards standard analogue servos because I only fly my plane at a sedate speed anyway - I have no need for super-fast reaction on the control surfaces. So to this end I shall soon bin the digital servos in favour of analogue ones. (Now standy and listen to the pro-digital brigade rip me to bits).
Good luck with your 8FG Super, Martin. I'm already betting my bottom dollar that you're going to be chuffed to bits with it.
