Serge Rousseau, A Canadian navigator, sent me some pictures of the installation of his iPad on his sailboat. He wrote me :
"I'm sending you some photos of the support. I fixed an industrial Velcro on the stainless steel tube and I maintain waterproof case (+or- 50 €) with reusable fasteners (Tie Wrap). You can also use a waterproof envelope used to protect the maps in kayaks and secure it with velcro and reustable ties. ”
For a particularly economical solution, I find it simple, clever and aesthetic enough for my own opinion. It's up to you to judge…