Richard,

VFP works well with Navision once you aware of all its little quirks when dealing with Automation. We use it all the time to supplement things like Navisions text fields being limited to 250 characters and memory variables being limited to 1024 characters. We currently use VFP 7 and 8 without any real issues.

Pegasus Opera II is completely written in VFP 6 and has a very good developers toolkit that enables you to pretty much subclass any form or class in the application. You can get a free demo version with sample company data from any Pegasus dealer or Pegasus directly.

Regards
Neil