Mountjoy: Thanks for the help. I will try the "fit x": at the moment we use "fit largest". I would of thought that if the loss of resolution was due to a scaling setting it would happen whatever the scaling used. A complication is that we supply a clean feed version in 16:9. Some say that for the end user a copy 16:9 or 4:3 letterboxed is the same thing, I'm not clear about it. Another input was the loss of resolution is due to ActiveX processing and that only the use of classic effects uniquely would avoid this.
As you are outputting both 16:9 and 4:3 from the same project, that was not the info given in the first post I think
my own workflow for doing this should be to work in 16 : 9 from the start, make all the edits and let it render.
Then create a new timeline 4 . 3 , select the scaling properties of the 16 : 9 timeline as described and drag it to the new 4: 3 timeline this way creating a container.
Others might use different workflows .