Hi Charles,
We have a 235 as opposed to the larger space of the 285, but would agree with Tom's idea. We have mounted our GPS and VHF DSC on a bracket on the bulkhead adjacent to the companionway. This swings out into the companionway when sailing and we can see all the data from the tiller.
It has other advantages, we can see all the info from inside when we are below, so you can input GPS data etc, when sailing you can see the screen and hear the VHF, and reach it to answer without letting go of the tiller. You can also take the valuables home and just leave the bracket and cables. It works really well for us.
Hope this helps
Graham Ebb
235/25 Blue Jazz