thermodynamics-GT exhaust tips

hello. the 88 gt vert is now painted. this question is about not frying or damaging the new GT bumper's paint.
my (stock location) tips end an inch or two inside the bumper, and are about the same height as the bottom of the bumper (one side sits so that it is visible from behind the car, the other is more tucked up).

anyhow, i have been contemplating cutting the tail pipes off and putting turn downs closer to the axle. the flowmasters are fairly close to the front of the axle; i dont know that i could do a decent job of putting turn downs up there. also for emissions here, they fail any car that they would have to "get under" to install the probe. (note: if this is deemed the best way to go, i could rig some pipes once a year. i would prefer not to).

the real question. i dont understand the heat and flow of exhaust out of the pipes. i am thinking that maybe as it is, the exhaust is dumped low enough and flows past the bumper, so heat is not an issue. but then again, the old bumper had baked paint adjacent the tail pipes.

would putting turn downs just to the rear of the rear axle keep more heat away from the bumper and paint, or would it cause more heat to be concentrated under/around there (i.e., would hot air get trapped there, whereas now it is scavenged out from under the car)?

you can see that i have some flawed logic here. please lemme know what you think and set me straight. i really appreciate it.

i cant afford the nice paint jobs you all have, and need this to last.

thanks for the reply, Ray. its a GT, so no straight pipes, a la LX. i should have mentioned (for LX people) that the gt's pipes exit just before the inside of the rear bumper (with turn downs). i think theoretically, the bottom of the pipes should be even with the bottom of the bumper facade. the pipes are suppposed to be hidden.

i never understood the idea myself. i know a lot of people run turn downs at the mufflers (i wanted to avoid it unless its the best for above-mentioned reasons). hence my wanting some ideas, experiences and principles. please share thoughts and ideas!. many thanks.
BTW, i hope i dont have billows of smoke coming from the exhaust.