Naaah. Just tried it - not a good way either. Sasquatch's method is good, except for the fact that a displacement is useless. The beveled SSS has to be plugged into a depth modulator to achieve best cloud slope.
However, I am thinking about yet one more thing...
Let's say, I use a whole array of SSSs (I do). I don't want to bevel-edge each one of them. Instead, how can I define a single point of reference, towards which the clouds would ascend? Hmmm... And that could be usefull for terrains as well.
EDIT: And here's a little infographic on how to achieve the effect. Note, that you can also easily warp SSS mask and successfully use it for both depth and area modifications.
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