I am sorry Steve, but truncating data without the user knowing is an error. It is frustrating that the source and target schema don't match, but it is still an error. Either the source data is wrong (swapped columns by mistake, etc) or the target schema is wrong. Either way: It should tell me that. A simple substring in the source query can fix it, if you are willing to lose data.
You've missed the entire point of the piece. This isn't about eliminating the error or silently truncating data. This is about ensuring the developer or DBA can find the source of the error easily.