I think incorporating volume into any strategy is absolutely worth doing - the problem is - when we do - it becomes almost a multidimensional problem.
For example, how do we define "low volume". Here are a couple of factors I can think of:
1. Low volume in winter, is different to low volume in summer
2. Low volume @ 5mins, is different to low volume @ 1mins
3. Low volume @ 1.50, is different to low volume @ 15
4. Low volume @ Lingers, is different to low volume @ Chelt
5. Does low lay volume, behave differently to low back volume
What an effin nightmare
A traditional hypothesis would be low volume suggests lack of conviction - suggesting a propensity for mean-reversion - problem is my gut says it's not quite that straightforward when it comes to pre-race (i.e. that would bias mean-reversion to occurring before the liveshow - considering volume is far lower hrs prior)
Perhaps the best way to gauge the importance of each variable - is to simply build a strategy around each concept (i.e. backfitted to time, backfitted to course, backfitted to price), then see how they compare over a week/month of forward trading