Hi,
The USPS plugin (
www.hikashop.com/marketplace/product/290-usps.html
) already has a "Sort shipping services" which you can configure to "cheapest" when you edit the shipping method via the menu System>Shipping methods.
However, I checked the code of the plugin following your message and I can see that the plugin suffers from the same issue that was reported for the UPS plugin 2 months ago:
www.hikashop.com/forum/install-update/90...on-issue.html#368578
So, I've made a patch for that in the USPS plugin. So, you want to update to the new version and check this "sort shipping services" setting. Then, you should be good to go. Note that the shipping method is preselected once when the shipping methods are first loaded. So, for your test, you want to reset the user session data by logging out and then logging in your frontend before testing again.