Ghost vs force shaft length

[outback_67]

I'm just getting organised to fit out a new bass boat, getting delivered in the next couple of weeks.  It will have a garmin ghost leckie fitted. Garmin shaft lengths work a little different to everyone else due to the way the cable spirals around the shaft immediately below the head, so the entire length isn't useable. I know someone with the same boat that runs a 47 inch ghost, but I'm unsure if this equates close enough to the 50 inch force. If I go to the 57 inch force is have heaps of length but also a lot more in the way when stowed. 

Does anyone know the actual practical comparison lengths between these two?