HI All
Long time user and little poser. :-)
I have no problem with using the levels whether it is SL or arbitrary. However, i do find that getting the levels to what is used locally would be best.
In Melb, the authorities likes to see it relative to SL or we call it AHD. For this, we have surveyor survey the site and relates the site level and floor level of the any existing building to the SL (AHD), and i simply set the terrain pad elevation referenced to the CA building level. ie, if my existing building is measured at 102.5 AHD, then this is my CA floor level of 00, i then set the pad elevation to 102500 (in mm above sea level), All other contours or spot levels i then call them up as require, ie 101.9 AHD will be 101900 in my spot level DBX (or elevation line Dbx).
This way, the levels that shows on the plan is the correct level when other people reads it.
To me this would be simpler then mucking around trying to reduce the levels of the site and relate it to the CA level or 00.
We try not to do any arbitrary levels that only relates to the site as much as possible.
Just my thought
Frank