If you use Expeditionpcb 2007.2/3/5, I think you will ofter get calls from your pcb vendors, they complains they find SIP(self-intersecting polygon) in your gerber data and thier CAM system can't get it repaired and sometimes they complain the data can't be read into the cam system. This is true.
If your gerber data in 5:5 mm or 5:5 mil format, CAM350 Pre-V10 often fails to read in due to the SIPs in the gerber data, sometime gerbtool 13.6 also fails. Orbetech's Genesis 2000 9.02 can read in those data but it can't correctly interpret it(some antipad will missed in plane and conduct to shorts).Even you set the format as 3:2 mm or 3:3 mil, you still can't eliminate the SIPs in your gerber output, however, it help to avoid Genesis 2000's interpret errors. Sometime, fab vendor ask you to provide R274D format instead of R274X. When you try to ouput R274D format data, you will find Expedition PCB don't support to generate Dcodes file automatically based on your design, so you have to creat one to get your film out. It's a time-cosuming and some of designer don't how to create a correct-format Dcodes file.Another problem is that you will encouter a very slow plane data generation if using negative planes.
To avoid these problems, You have to trim the cell to keep not exceed 2 digit precision.