When using HBase as a source for MapReduce, can I extend TableInputFormatBase to create multiple splits and multiple mappers for each region?

I'm thinking about using HBase as a source for one of my MapReduce jobs. I know that TableInputFormat specifies one input split (and thus one mapper) per Region. However, this seems inefficient. I'd really like to have multiple mappers working on a given Region at once. Can I achieve this by extending TableInputFormatBase? Can you please point me to an example? Furthermore, is this even a good idea?

Thanks for the help.