#19DO.... i did the normal CL 2 outline form on 19 D0 , after that i removed the distal cusp because there is so called undermind enamel at distal cusp. Normally lingual side exit angle is ok and clearence is about o.5 mm , but buccal side exit angle have problem from pulpal floor to the occlusal cavo-surface angle , there is undermind enamel (due to enamel rod direction) from exit angle to the distobuccal groove, so that u have to remove all the undermind enamel until the groove reaching to the disto buccal cusp.
Finally u have to cut away entire distal cusp, leaving big space / clearance in buccal side from occlusal to the pulpal floor. Normal exit angle 0.5mm for the pulpal floor to the gingival floor. For that prep , amalgam curving is difficult too, pay extra care for the inter-proximal curving.
u can find in book STUDERVAN ( not sure spelling), page 455 reduction of cusps .
if you want to know more detail, pls contact to my instructor DR : Ryan Thaw.