Well after contemplating every cup holder known to man as well as every location possible on my boat and tipping bottles and cups over for years, I finally pulled the trigger. Keep in mind I am the original owner so it is safe to say I procrastinated a bit on this project. I installed a stainless flush mount cup holder on the dash of my 518vx. If you are not aware this boat was built with 1 cupholder. A pretty disappointing location and product considering it is a Ranger. The original "built in" cup holder is on the side wall next to the passenger. When flipped down the passenger rod ramp is kind of useless as all the rods get tangled in the flip down claws and base.
Here it is, I moved a GPS puck to my splash well area then cut the hold for the cup holder. The cup holder install also served as a cover up for the old GPS screws and hole as it installed in the same place. Beneath the dash I used some neoprene tubing to route the water down to the belly of my boat, the cup holder has a drain in the bottom.
https://www.flickr.com/photos/140680.../shares/8mH02Z
Seems like a silly thing to give a person so much pleasure but just having that cup holder makes me not have to worry about where my coffee cup is or am I going to tip it over.