relocating rear flu to top flu- Issues?

I second the baffle plate to prevent more heat rising directly out of the stove.

More info here; https://www.hearth.com/talk/threads...less-smoke-under-25.74710/page-4#post-1748825

The first (Fisher) steel plate stove was side vented to sit across the hearth and not extend out into the room farther than necessary. Then they were built with rear or top vent. Baffle plates were developed for double doors around 1980 but were never used on single door stoves.

The main thing is that you make the new collar long enough to extend down into the stove. Length was 5 inches long, extending into stove I believe 3 inches. That way the rising heat goes to the top and has to be pulled down to go up the stack. If the flue collar is even with the inside of stove too much slips up the flue.

Keep the baffle plate "smoke space" or the square inch area the exhaust flows through at least the square inch area of the flue outlet on stove. No smaller. And use a damper in the first section of pipe if possible.