exhaust under gas tank

[my56chevytruck]

OK, I'm close to driving my truck and need to have my exhaust put in. we have a great exhaust shop close by, but I'm wondering about running 2 1/2" pipes right under my gas tank. I can run the pipes within the frame up to the tank but to avoid the gas tank I'd have to go outside my frame rails to go out the back end. My 31 gallon tank is out of a suburban and is mounted in the rear end of the frame and is hanging partway below the frame. I've read a lot about the pros and cons of doing this, but wanted the forum's opinion.