Phil; I don't have a downrigger
. Don (Hunter) runs a poor mans downrigger with a stick off a double "outrigger" off the gunnel closest to the motor. The "stick" is only about two ft long (maybe like the arm on your downrigger). I wouldn't want it any further forward.
I run outriggers off the side gunnel but have a six ft rod extending horizintal to the water. This puts my lines out far enough to not have to worry about making turns and the line near the motor. If your arm is not very long; I wouldn't put it forward.
I agree port side for visability
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But before I drill any holes, wait for a response from either Don or Skip.
5th (Marty)