Fedex doesn't work, UPS only works with one dimension!!!!

I'm so disappointed with OpenCart shipping system. It took us 2 hours to set up a Fedex account and get the keys, meter#... and it didn't work due to Opencart technical problem then we created a UPS account and figured out that it only work for one pre-defined dimension (the average packaging dimension) and also not all UPS services are offered (such as UPS freight) which cause waight and dimension limitations. We have so many products and OBVIOUSLY each of them has different weights and dimensions and each one will be sent to different regions in USA. Is there anyway that we can integrate with Fedex or UPS or USPS and use their calculation method? their calculation is based on either "weight or dimensions" and "From & To"