I'm using SGL, which makes heavy use of the slave SH2, so it's not an option. Even in Sonic R they scrapped using it ingame, probably because it was too intensive for such a little effect.
If I were to use software rendering, it would be for something such as transparency on the NBG0 or NBG1 layer, using them as framebuffers.
And only if I could use the SCU DSP or sound cpu to do it.