I just realized something that maybe could be improved.
The instructions CMPS and CMPSX actually report a 'signed carry' into C (the spreadsheet wrongly said 'overflow'). However ADDS/ADDSX/SUBS/SUBSX do report 'overflow' into C.
I'm thinking that for consistency, CMPS/CMPSX/ADDS/ADDSX/SUBS/SUBSX should all report a 'signed carry'.
An 'overflow' report only makes sense for SUMC/SUMNC/SUMZ/SUMNZ, I think.
Any agreement or disagreement?