Would have +past participle if +past perfect/simple past(?)

Hi,

Is this sentence correct?

As I listened to Ian (who now runs backstage) I kept wondering what I would have added to the debate if I was in his position during the recording.

I've been tought that I should follow this rule whereas a  type III conditional  is concerned.  "I would have +past participle if +past perfect".(I would have come to the concert if I hadn't been sick ).

Can I replace past perfect with simple past?

regards Cavillous

This situation is a little different than your type III conditional formula is intended for.  The speaker is not in Ian's position, so the phrase is a "condition contrary to fact".  In that situation a formal speaker or writer would use the subjunctive mood of the verb rather than indicative or imperative, so the phrase would read "...if I were in his position..."  In the subjunctive mood there is only one past tense form of to be, and that is were.  Another example of subjunctive is in a request such as, "We asked that she drive more slowly."  Usually it would be drives, but in this case the verb does not change to indicate the number or person of the subject.  Many speakers would say drive instead of drives here, but would not know why.  That's just the way they have learned to speak.