Bought a Yamaha CPX900 yesterday. Got it home and thought pretty easy to lower the action. I shaved the bottom of the saddle a bit. Tightened up the truss rod a bit and to me anyway still seems a bit high. Mind you I like a very low action on an acoustic similar to an electric. Played around with it all day and best I could get it. I can't take any more off the saddle or the strings will be going over the bridge wood. There is no noticeable belly bulge but I put a straight edge across the top of the guitar behind the bridge and it is not 100% flat. The bridge isn't tilted forward or anything like it is under strain. Looks flat on the top of the guitar. Just sort of raised slightly where the bridge sits. I guess you would fit a coin under each side of the straight edge at the edge of the guitar. I took it to a local luthier and he said this model guitar is not meant to have a 100% flat top and he thought the action was pretty normal. He put a light and mirror in the sound hole and said bracing was sound. I reckon there is about 3mm at the 12th fret on the low E string. The lowest I can get the action is with the truss rod tightened so the neck is slightly concave believe it or not. I have 11-50 strings on it. I tried 10's but weren't a lot different. Come to think of it I have only ever had one acoustic guitar with a super low action in the past, an early Japanese Takamine. Was like silk to play. Neck so straight. About 1mm strings off the frets all the way up the neck and no buzz etc. Am I being unrealistic. I know a better tone is probably achieved with a higher action but I wish I could lower it more. I have played around with the truss rod to lower as much as I can without buzzing and taken as much as I can off the saddle. I guess the Luthier should know however I am not 100% confident this guitar is meant to have a slight arch. What do you guys think? Been doing my own set ups for years, mostly electrics but this one has me stumped.