Hi Drupal Junkie,
Glad you like our forum!
Here's how to setup tiered flat rate shipping in Ubercart using Drupal (you almost had it right, btw):
Browse back to the Ubercart quote methods page. Then, click on the "flat rate" sub-menu link and select "Add a new flat rate shipping method."
In the next screen, give your shipping method a unique title to help you remember what it is (ie. "50 dollars and less" for your $50 rule). Next, give it a label that your users will see (ie. "ground shipping"). You're going to give all your flat rate shipping methods the same label, so users won't be picking different methods because the only distinguishing characteristic will be price.
Next, set the base price to that of your shipping method floor (ie. for "up to $50" enter "0", for "between $50 and $100" enter "$50"). Next, set the default product shipping rate to 0 (this is probably what was causing your shipping rates to sum together (add up)). Finally, hit "submit" to save your shipping method.
This will take you back to the quote methods > flate rate screen where you'll see the shipping method you just created. In order for the shipping method to kick in only for a certain cart balance ($), you'll want to click on "conditions" next to your flat rate method (ie. "up to 50 dollars").
Now you're on the conditions screen. This is where we're going to set your various price/ shipping thresholds.
Add a condition for your lower limit under Order > Check the order total. For your first rule, "up to 50 dollars," you'll want to enter "0" as the "order total value," and check "total is greater than or equal to the specified value." Save your condition.
Add a second condition for the upper limit. Use the same setting as above, but this time set the "order total" to "50" dollars, and the "order total comparison type" to "total is less than specified value."
Save your changes to finish your first flat rate shipping rule. Rinse and repeat for the rest of your rules. When you're done, your buyer will be presented with your "ground shipping" option, which will automatically apply a shipping cost based on your buyer's order total - ie. via the tiered flat rate shipping rules you created.
