Hey Ralf, when you say that the feederhouse on your 7720 is the same width as an STS are you talking about overall width or width of the actual opening. Because all Deere combines from the past 30+ years have the same width of feederhouse on them. That's mainly so newer combines can still hook up to the older heads. But each model has a defferent width for the actual throat, or opening. Our 9650 has a smaller throat than a 9750 and so on, but same feederhouse. And 2366's have a smaller one than a 2388. So does a 7720 compared to an 8820 or an M2 to an L2. But they can all hook up to the same heads offered from the manufacturer.
And while 2.5 bushels per second may be good for this 7700, since as combiness says it originally came with 1.5 or so, its still very slow by todays standards. And this guy is making it sound like this combine can run with the biggest and baddest on the market right now as far as capacity. So if it has that kind of capacity I say that 200 hp and 2.5 bushels per second isn't quite enough, especially compared to combines today. But for a 7700 I'm sure its quite a bit.