Looking good Paul.. As you say, could be brighter, but it definitely looks the goods thus far!
With the Lum layer, As Greg said, the C filter is the go... as you can amass some serious data really really quickly that way.. I'd blend the C data with the Ha, and also blend the Ha say 30/70 with the R channel... So you'd have L+Ha R+Ha G B mapped as LRGB... That way you'll really give it a good strong Ha kick whilst also having tons of data from the C filter, and maintaining the colour balance in the reds... Its a constant game of trial and error I've found...