With the small space under a jack and jackstands, I had the same problems. I couldnt get each section rotated to the perfect positions and due to the bad angles I couldn't even get the tips on. Broke down and took it to a muffler shop, they threw it on a lift and had everything right in less than 10 minutes.
Looks good, sounds great, just was a pain to install without a lift. These weld blowouts I keep hearing about worry me though