Hi Scott,
A good way to balance the colours is to choose one as the reference, say Ha, and then apply LinearFit to the Oiii and Sii. Then do the colour combine and you'll have a much better balance as a starting point for further manipulation.
Also worth trying Colin's suggestion or H's. Lots of ways to skin this cat
Also FYI, SCNR has a much bigger effect on linear data than it does after a stretch.
Cheers,
Rick.