Earlier today I posted about the spatial and temporal ventriloquism aftereffects. One of the reasons I find those effects fascinating because I think they might hint at a counterargument to recent studies by Daniel Casasanto and Lera Boroditsky that seem to provide evidence that time is metaphorically structured through spatial experience and concepts, as I discussed the other day. In those experiments, the growth of a line and the length of a line influenced people's perception of temporal durations (see the link for a full description of the studies). I think this result might occur because we're not very good at estimating duration from visual information, so the brain relies on what it does well with visual information-- spatial reasoning -- to help it do what it doesn't do well with visual information-- temporal reasoning. If that's the case, then we would predict that the reverse would be true if the stimuli were presented auditorily.
To test this prediction, we could present participants with two auditory stimuli (beeps, say) spaced at different distances, and occurring at different temporal rates. Since the auditory system is better at temporal reasoning than spatial reasoning, we'd then predict that people's estimates of the distances between the locations of the beeps would be affected by the temporal rate of the beeps, because the brain would be going with what it knows how to do best with auditory stimuli. Faster rates would lead to smaller distance estimates, and slower rates would lead to larger distance estimates. If that occurred, it would make it difficult to argue that Casasanto and Boroditsky's results provide evidence that spatial experience and concepts metaphorically structure temporal experiences and concepts, because it would show that the "structuring" is not asymmetrical in the way that the metaphorical structuring view predicts.
If you do get your proposed results, maybe its a cop out, but could you not just say that the conceptual structuring of time is based on how the visual system represents space, and not by the auditory system represents space?
To make the task closer to the C&B task, how about two beeps spatially separated that beep simultaneously or separately, and you have to judge both the length of time of the beep and the distance between them. Based on your explanation, you should find short beeps associated with short distances and long beeps with long distances, and that we would overestimate distances with long beeps and underestimate with short beeps?