Mass Finishing Suggestions

I'm looking for some mass finishing equipment and process suggestions. I currently have a 3 cubic foot vibratory and a home built spindle/drag finisher. With plastic media the vibratory is causing too much edge rounding and isn't leveling the scallops on the sides of the undercut sections. It doesn't seem to do anything to the deep sections on the middle of each side. The spindle machine is too light weight to handle plastic or ceramic media. It will hold about sixty pounds of corncob. I've had good results with it using a couple grades of cob and flour. The flats and corners come out beautiful but the deep sections are untouched. I've been thinking about building a bigger spindle machine and increasing the mass/sfm of the media or a build a centrifugal barrel. The pics show an as machined part and one that has been done by hand over the period of a few days. Polishing is getting old. Do you guys have any suggestions?

Thanks,
Kevin