Mucked around re-building with this today.
Liked this shape but wanted shorter:

got rid of this junk inside:

tacked up the size I want:

what do you think of the above baffle? basically one of them chopper baffles cut in half and then shunted off with a plate so everything has to flow out and then back in again. Seen other do this with the perforated baffles, so presumed this might be worth a go? Thought I would get your thoughts before welding it up.