[knuterikt]

I use this solution called cableport.

I like this solution as it is easy to add more cables later and you can pass plugs through the opening.

Picture with top off

Picture with top mounted

Pictures from the producers web site found at Elvabro AB Marine

 

[knuterikt]

It's not obvious looking at the posted pictures but the edge on top of the tube is well rounded as you can see on this illustration.