I would add on your pad to roll it in one direction and on the next pass roll it 90 degrees from the previous direction. Also over lap the drum from the previous pass. CM1995 is right, getting the moisture content correct on straight clay is no easy task. We seldom have that kind of material in the high desert, its mostly 8" minus pit run. Much easier to compact, and optimum water percentage isn't as difficult to find. If the soil your compacting is bone dry, I would scarify it first once your first lift is laid in. Then add water and relevel, otherwise the top of the lift is wet but its bone dry under it, making compaction misleading, good on top but not so much below the top 4" or so. CM is also correct on it being a science. Lastly, once you have developed a good routine that achieves good compaction. Don't vary from it, do every lift the exact same way.