I'm fairly certain this operation was working, but now the button for "Make object double-sided" appears to be disabled. It does not appear in the Options->Operations tab.
1. Create a cube 2. Delete a side 3. Select cube 4. "Make object double-sided" is not enabled
NOTE: "Double side" causes Canvas to crash a lot in 6.5 and earlier when it runs. Richard says he thinks he knows why. It might be fixed in the future.
I got it working after a re-install... but, from that point on (after I use the double side operation) Canvas 6.6 is unstable and will crash. It has even ruined a 3dc file more than once as a result.
I did finally get to this. I believe I have a solution. I was having lots of problems with my Merge Faces plug-in and hunted down the cause.
The positive is the Merge Faces plug-in runs about 10-20 times faster on complex models, and no longer leaks memory. Many other plug-ins will run much better as a result too.
The negative is that it is quite possible that MANY plug-ins were broken as a result. Materials are now semi-object based and this can cause problems. It caused my MergeFaces plug-in to stop working.