If it is an open hole in the baffling doing nothing, then absolutely yes plug and seal it. I am not an AA-5 owner but I have never seen anything on the right side rear baffle other then the hole that the lower plug leads come through (and that should be well sealed).
Other then some pressure mags which these series have not used, the only other thing I can think of that there might have been a hole with a blast tube in the past was I think it was a Tempest vacuum pump that recommended a cooling tube.