I tried adding a tray years ago to a customers engine after we dyno tested it...he set the hyd. clutch up a bit wrong once in the car and drove it about 5 miles when he noticed excessive noise at the back of the engine, so he pulled it out and brought it back to us to check it out...we replaced the main and rod bearings, and added a tray, then did another dyno session...with NO gains! This was using a Milodon 7qt pan, so the oil was lower than most other pans (about the same depth as the RR pan) and we always recommend running the oil level between the add mark and full mark.
If you plan on running a near stock oil pan, then a tray is going to be more functional, so it really depends on what you plan to do with it.
