The two referees were in agreement that the paper should include a model of migration of inclusions. The authors' response indicated that they were reluctant to include a model of this type, but without this model, the referees' ratings indicated that both felt that the paper lacked original content that would merit its publication in TC. As it is, the manuscript validates a new ray-tracing model, but without demonstrating a sufficiently novel application of this model, it makes only modest improvements on the existing I recommend that the authors resubmit the manuscript once they can quantify the downward migration rates for inclusions.

Sorry about the delay after referee #1's second report. This looks like the referee is much happier with the manuscript now, subject to some very minor concerns. Please send a revised MS at your convenience.

Thanks for a quick revision. This seems to clear up the questions in V2.

All the best
--Ben