Thank you! I can see where the logic comes from, but keeping in mind that a round is two seconds long, I doubt one will have time to perform a full shield bash while parrying. Those things are heavy!
First off - unless the character has a skill or a spell that allows for two attacks per round, then they cannot, in any fashion, parry with a weapon while performing a shield bash. That is the point of what I quoted from the rulebook (how the shield bash takes the place of the normal attack action (and how a parry is part of a normal attack action).
You ruled correctly.Secondly, If a character has a style that allows for shield bashing and fighting at the same time, then the weight of the shield doesn't actually matter since the character would have been trained in using it in such a manner, and thus used to the weight factors involved. However, when using such a style, if the character reduced his OB to parry with the weapon, then he would also reduce his OB with the Shield Bash (which we are presuming your player did not want to do... heheh).
According to the information you gave us (skill in Long Sword, and Shield Training, but no Sword & Shield skill), then character would not be allowed to parry while performing the shield bash for the simple reason that the shield bash replaces his normal attack.
Put another way, if he does not make an attack with the Long Sword, then he cannot parry with it because a parry is
part of an attack.