I got tired of having loose wires in my car so I hardwired my GPS.
My dash looks much cleaner now
Remove the waterfall (there are several posts about doing this)
I purchased a cheap ($4) lighter plug splitter and cut one of the outlets off, then connected it to a wire that I had tapped into the fuse box with. I used a switched circuit so it automatically goes on/off.
I then pushed the lighter plug power supply for the GPS into the outlet and thoroughly taped it so it cannot come apart.
I then stuck the whole assembly into the hole in the center that the wires come out through.
Then route the power wire up to the top. You can replace the waterfall with the wire sticking out of the top. I then stuck the round flat Garmin mount with the double sided tape just above the hazard switch. The suction cup mount sticks to this (I tried without using this and it would fall off after a while) Make sure you clean that area with alcohol so the double sided tape sticks.
Then just mount your GPS.
The screen shot on the GPS matches what you see out the window, Lake Michigan