Fees at order level: preventing 'double up'

We're in a situation for the next couple seasons where fees will vary by performances.  One group will have one set of convenience charges per ticket (rule-based fee set at the performance seat level) and a handling fee per order (rule-based fee set at the order level).  The other group will have these exact same type of fees, just at a different rate.

The problem we're seeing (and we've run into this in the past when transitioning between fiscal years) is that when a patron purchases tickets for two or more shows from the varying fee bases, the handling fee (rule-based fee set at the order level) is being charged twice.  As you'd imagine there is no issue with the fees set at the performance seat level, we're good there.

How can we avoid this 'doubling up' of the handling fee?  We have it set so the user selling the tickets can override one of these to zero but that really isn't the ideal solution considering the the time frame that we'll be working with these dual fees.  Especially considering we do online sales and, as it currently stands, there is no way to keep the patron ordering via web from having to pay this fee twice when adding shows from both fee pools to their cart. 

Any suggestions?

Thanks!

Dave