For top cinched: I use a RB with a Y....though after reading this, I think I'll start double overhanding around the line. Redundant safety is always a good idea.
Bottom tied: 80% of the time I run it through an 8 that has been cow hitched to the tree then hard locked....then locked again with a biner through the figure 8 on a bight and around the line. Why not take the extra time to save time during a potential rescue with myself as the victim? As much as I love my groundies....well I'm not an everyday climber, they certainly aren't. Not trying to highjack the thread, but am I the only one that does this semi regularly? If you are wondering about the other 20% of the time....it's because my rope wouldn't be long enough to lower me. In which case I use a half hitch, then the RB with a Y.