Screwless head unit mounting

Looking for ideas on how to mount a graph without screwing into hill. I thought about the suction cups but the surface I have isn't flat. Is there an RTV or something that will hold but can still be taken off with a little effort. Thank you

Would think if it could be taken off with little effort it wouldn't hold the graph very securely when bouncing across waves.

RAM Mounts makes ball mount bases that clamp onto handrails or other objects and don't require screws as well as a suction cup mount and maybe other styles that don't need screws.

http://www.rammount.com/components