Volvo Amazon Side Pipe muffler position

Hey all. I have a slightly built Volvo B20 in my Amazon coupe. I built a stainless steel side pipe that comes straight out of the header, turns 90 degrees, and exits in front of the rear wheel. As expected, way too loud. I bought a stainless straight-through muffler, and Im wondering how far back from the header I should install it. Ive read mixed suggestions, saying as close to the exit as possible, or as close to the header as possible. Any advice? Thanks
Picture of exhaust off car:

I believe you are going to want it as close to the exhaust exit as possible, generally speaking putting anything near the collector of the header is a bad idea. Ping Vintage Wrench here on the forum for his setup on his P1800.

Even with a single straight-thru muffler it’s gonna be pretty loud. I’d agree as close to the exit as possible will be ideal. There really isn’t anywhere to put one other than the factory location though which probably won’t work well with a side exit. Why not just route it under the rear axle and out the back? It’s a few more bends and isn’t going to hurt performance.

https://flic.kr/p/TjnxqL

This 2-1/4" Boria straight thru muffler that is slightly angled-internally has worked well on our '67 1800s for both racing at tracks that have sound regulations and for road use. When we can run an open exhaust at the track the muffler is replaced with a piece of tubing.

Its not that loud at idle or on the street if you keep your foot out of the throttle as much as possible, but gets it gets noisier the more you open it up.

What is the reason that mounting a muffler near the collector is a bad idea? Heat? And the reason Im not running a traditional exhaust is that my car is on air suspension, and the gap between the body and rear axle is too small to run an exhaust through it when on the lowest setting

Run it under the axle?