I created a custom pipe rule a while back, but I couldn’t find were I placed it. I found it here:
The rule checks the separation distance between incoming pipes as well as the minimum wall OD for the structure based on the manhole wall thickness. It pretty much checks the design similar to the requirements found in this manufacturer’s sizing chart: http://www.cretexnorth.com/Catalog/ercp/ercpmhcbsizingchart.htm
With the new capabilities within the API I think I could revise the rule to have the rule change the wall thickness to be the correct value. Not quite sure if I’m going to do that though, but at least you’d have a warning message. I also should convert the rule to .NET.