Croys, thanks for an excellent reply.
Sigh! I'm beginning AP might be an exercise in frustration in Singapore, especially DSO imaging.
Still, I managed to get my hands on a pair of Astronomik UHC and OIII 2" filters so I guess I've give those a go

Cataclysm: Thanks for the offer. Unfortunately I'm using a Nikon

I might borrow Kochu's filter to try though on nights that permit. The nice thing is that my NE sky overlooks Johor in the direction of Punggai, so its relatively dark. I haven't measured apparent limiting magnitude yet since its mostly been hazy/cloudy but on a good clear night quite a few stars can be seen at zenith, so that's a hopeful sign
