If your SuperTracks are cutting off too soon with a 2 bar ending, use this workaround. Add the RealTracks Silence (#1152) to an unused part in your song. You can also modify the style(s) to contain the Silence RT. Make sure the RT Setting 'Use 4 bar ending for songs with RealTracks' is checked. Now your 2 bar ending (including SuperTracks) will extend to 4 bars.

I posted the SuperTracks 4 bar ending on the Wishlist forum. Hopefully, it will be considered.