How to stop fallback from H+ to 3G data

**Is it possible, and if so how, to lock the phone to using H+ for data and not dropping back to 3G?** I suspect it isn't (firmware of the radio hardware I'm guessing) but there's times where I would be willing to take the battery hit to keep my data on H+ (specific application with data demands that doesn't like dropping back and forwards to 3G). **I'm not talking about changes in signal quality:** I can be sitting in a single location, not moving, where both H+ and 3G are available. When data is being requested the phone typically goes to H+ as it is faster. Once the data demands reduce it drops back to 3G. I have read in a number of other places that this is on purpose to save battery. However my issue is that one app I use doesn't handle the transitions well so I'd like to stop the auto-fallback. Android 4.2.2 on Samsung Galaxy S4 mini, Australian networks.