Several years ago my lifelong shooting buddy was actually making rifled choke tubes for one of the major players. I had many occasions to experiment, make suggestions and assist in the design.
After a lot of experimentation a couple of things became quite obvious.
Back then Fosters were pretty much all that was available..soooo. You fire a SOFT lead slug in your smooth bore and it reaches maybe 1200 to 1400 fps, all of a sudden you slam that SOFT lead slug into a rifled choke tube that is maybe 3 to 4 inches long. Mostly all the slug does is skid across the rifleing.
The groves and lands in the choke tube are far too small and light to capture a SOFT lead slug and reliably spin it with any accuracy. It is a fact though, ANY amount will stabilize a projectile MORE than no spin whatever.
The bottom line is, I guess from my several years of testing various rifled choke tubes is that any improvement is absolutely minimal to non existant.