Just to add my 2 cents here- A module that would be a solution to the scenarios depicted here ***Really Is Needed ***by quite a few Zen Cart owners (yours truly included). There are plenty of threads that decry what someone else above called "the Drop shipper’s Paradox" (very appropriate moniker of the problem).
The only viable solution I've seen is a 'Pay For' Module (not free) that is lately at around $68.00 given the current rate of exchange (British Developer has it priced at £47.50).
I haven't tried it personally as I'm still hoping to find a less "do everything imaginable" solution (and a free one would be nice) but I have seen others sing it's praises. That 's why I mention it- maybe others will be helped. It's at http://dev.ceon.net/
For my purposes, all I need is to be able to charge one set of products on a flat scale (product cost $0 to $10.00: will have a shipping rate of $5.95, $10.01 to $20.00 will have a shipping rate of $6.95, etc.) while still being able to charge my FedEx calculated (by weight) rates for all other items. Anyone have any ideas? I'm no programmer but it doesn't seem like it should be so difficult (i.e. Zen Cart's one size fits all way of doing shipping). But again- I have no knowledge- maybe it's *very *difficult. Thoughts?