CobraStangGT16

Hey guys, tomorrow I pick up my Magnaflow stainless steel 3.5" 45* slash cut tips. They connect to 2.5" pipes, which is what I have.I have a few questions:

Heres the part if you wanna check it out: http://www.magnaflow.com/02product/s...ain&id=725
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Do I HAVE to weld them on? Or can I just use the supplied clamps?
Do I sawzall the stockers off, then just overlap the Magnaflows over the stock pipe?
How can I make sure they will be even? My left side sticks outabout 1" more than the left right now
Are 3.5"s too small to go from 3"s? Should I have gone with 4" tips?
I ordered the 18" long ones, not the 22"s, did I get that right?
Is it OK to sawzall/clamp the Magnaflows right before the pipe begins to bend inwards and go over the axle.[/blockquote]
I don't have access to a welder, so I'll need to use the clamp-ons. I can get them welded if I MUST do it, but I'd hate to pay somebody to do it.

Again, never done this before, and I'm sure I will have some problems. I'm nervous, but pretty happy I finally got them. I'll post pics tomorrow if I get it done.