That is interesting Sprike, but it seems like you are throwing away a degree of freedom for a little extra length. I often fish with my rod crossed in front of me and I want to be able have it be higher like so.
You could not do that with the fixed arm on your boat. I guess it is a tradeoff. I am 6'4" and have long arms for my height so the extra length on the arm is not needed. I personally feel that they extra flexibility of where I can place the rod in a 3-dimensional space is important.
Fish tremble when they hear my name
A ship in harbor is safe -- but that is not what ships are built for.
--John A. Shedd, Salt from My Attic, 1928