Put Daria to work on a thorough cleaning. Just what little sisters are for!
Finally, as I contemplated smoothing off the top of the bases, I got the inspiration to instead carve a socket or saddle 1 inch deep into the base to hold the springer. This would provide the esthetic effect of making the springer appear to "spring" out of the rock, but more important to me was that locking the springer into the base would obviate any need or concern for further buttressing.