Hi George,
with my version of the Helix, i did 10 hrs of Ha and 8 hrs of Oiii
http://www.aapodx2.com/2016/20161009.html
these were 20 min subs and it seemed to work though your set up will be completely different. i actually found that i would have liked more Ha data, there is no need for lum, but the more Ha data you can get the more you can bring out those fainter outer sections of the Helix that are spectacular. it depends on what the focus of your image is, if you want to capture the detail structure on the inner ring, go with more Oiii data, which is what i ultimately decided on. i didnt use any RGB data for the stars, if you want them to be anything other than white then you will need to do that