Combating Pollution with filters

[Robfal]

I've now almost got my observatory sorted (some guiding issues with Maxim) However I now want to look at improving image quality and reducing light pollution is an obvious area

I currently image LRGB (Atik USB filter wheel with the fifth slot blanked for Darks)

My options are

1 Buy a narrow band Ha Filter; this would only remove the pollution when used (perhaps instead of the L)

2 Buy a general Light pollution filter (eg Lumicon Deep Sky Filter or similar) and stack it on top of the other filters

There are advantages for both options. The Ha filter would allow me to image in moonlight whilst the other system would reduce the pollution in all subs.

I understand the Ha is very good for Nebula but what about galaxies?

How well suited is the Lumicom to imaging? Does it matter if there is some pollution in the RGB channels if the detail is added in the L layer and the others are only used to paint the colour in?

If I went for the Lumicom option (there are other similar filters) where and how should I put it. Would a 2" one screw onto the Atik Filter wheel or would I need to adapter?

Many thanks

Rob