I used to have a 605 combo. Shot the single barrel better than any other gun I've ever had. That is until the rib popped off. I was shooting one day and started missing EVERYTHING. As we were walking off the field after the 25 was complete I looked down and there was at least 1/8" of air between the rib and the barrel. The rib was stil attached at the ends, but had come loose in the middle. I sent the gun back to Japan and they reattached the rib, but the gun never shot the same again, or maybe I just lost confidence in it. I sold it a few months after I got it back.
That being said, if I were to find another one that fit, I wouldn't hesitate to buy it. I think that the ribs were epoxied on the barrels and the cleaner that I was using just dissolved the epoxy over time. I'd be careful with the cleaner I used on the barrel, but aside form that I'd have no issue with having another one.