For crimping of aluminium or hard-drawn copper (common in XLPE and other cables), Cabac recommend crimping with the standard die for that size, then crimping a second time with one half of the same die, and one half of the next size down. That is, for a hard-drawn 90mm2 cable, you would crimp first with 2x 90mm2 dies, then a second time with 1x 90mm2 and 1x 70mm2. This can also be applied to aluminium conductors, but varies based on cable and lug.
Depending on lug thickness and cable conductor overall diameter, stepping down a full size may be required for a satisfactory crimp. However, care should be taken to never crimp too small a size, resulting in the lug splaying out with flat 'wings' on either side of the crimp. This indicates that the lugs overall thickness has been reduced, and will no longer be rated for its maximum current.