Great work Rob.
Don't be afraid to also use longer subs for you RGB data too. Don't need to be as long as your lum/ha subs, but you'll improve the richness of the colours and reduce noise in the process.
Your colour balance looks good, but you've got an distracting blue cast over the image. When I analysed the image in PS using the equalize function (Image | Adjustments | Equalize) the extent of the blue cast is emphasised so it is clear to see how far the cast is distributed over the image (see first attachment). When looking at the histogram in the second attachment you will note the blue channel does not align with the R and G channels. In addition to this, the main histogram does not indicate any black clipping is present however when you go into the Levels dialogue box, both R and G channel are actually black clipped while the B channel is not. The clipping of the R and G channels is the cause of the blue cast. You may need to reprocess this one.
Also, is this lum the Ha you capture of the object a while ago or is this new data? You're Ha luminance was great, so it would be worth combining this to some extent, providing you can keep the colours well saturated (considering the very long exposure time for the luminance compared to that of the chrominance data)
Cheers
