>I am doing a Show Heavy rotation right now, and I am finding
>my biceps to be the weakest. When should I work them to get
>optimal results?
Are you basing this on the amount of weight you can lift with them vs. Cathe? If so, realize that, from what I've seen, Cathe often goes heavy in biceps and light in back, so just because you can't lift as heavy as Cathe in biceps doesn't mean they are that weak. We all have different strengths and weaknesses, partly due to the leverage we have.
I don't see any reason for working the biceps first unless their is a discernible weakness in them. If that's the case, try working them first ("priority training") once a week or so. Realize that when you do work muscles 'out of order,' work for the larger muscle groups may suffer, because their agonists ("helper" muscles: biceps for back; shoulders and triceps for chest; triceps for shoulders) can't help as much. If you do mostly isolation moves for the larger muscle groups, the weakened agonists won't have as much of an effect as if you do compound moves (that usually use them), but isolation moves are less functional, and compound moves help build the body proportionately.