Hi Katie,
Sorry for not getting back to you. I got sucked into a number of things. We actually went with a slightly different implementation that fits the product data by most of our customers (book publishers) better. A lot of them don't have complete Height data and since the shared packages out out the dimensions anyway, we decided to just bypass it in call cases instead of asking the publishes to update all their products with complete and accurage dimensions. We changed the code to not only send "Variable" and "Regular" for shared packages but also if there is only one item in the basket.
We did make some modifications to the uspsmethods.csv file to prevent publishers from using flat rate ship methods without consulting us first because it's vital that they settle on only one of the flat rate options. All this seems to work just fine. If you like, I can send you our code (the USPS.cs). I think the basic changes are the same as you made.
With the last round of USPS changes earlier this year we made some additional modifications to use a "stop word" list for filtering out specific pieces of the USPS response XML that would require exessive setup by the publishers, e.g., having to set up 5 shipmethods for the priority to have all the possible response versions covered. Of course, if a publisher wants to display the delivery date commitment data, it can be easily set up for them but we avoided a bunch of support calls of "missing" shipmethods for shoppers.
Anyway, it alls seems to work just fine and I'm testing the second version patch today before we upgrade all the sites.
Thanks again for your help. I had kind of hoped that you guys had a better idea than we did for how to work around the box size selection problem (like come up with a brilliant 3D Bin calculation code for shared packages

) but what you did which mostly matched ours works fine. Let me know if you want me to send you the USPS.cs somehow.
Have a great day!
-- Karin