If you have slopey charts, then your folk may need to have a beer and reconsider what they are trying to do. If the envelope is not boxy then the sheet is not as good as it could be ...
In general, the slopey charts are the province of the GAMA fraternity (largely because the GAMA standard format follows the ICAO recommended practice .. ie both are a bit silly when it comes to loading systems). The heavy metal brigade generally use a more suitable trim datum for trimsheet design. There's naught difficult or fancy about this stuff .. all quite straightforward once you get the hang of it.
Quite happy to send you a sample sheet (for my sins I have done more than a lot of these little joys) ... do email me and we can discuss offline ... engineer to engineer ...