I understand the Ratio spread your talking about, 3 x NAB is...

I understand the Ratio spread your talking about, 3 x NAB is about $73- vs CBA at $72-

For me to assess if I think thats a Viable trade I would need to know what timeframe your trading and assuming you cant trade inside 30 days I cant see how you could repair it if it goes against you.

But assuming you can jump in and out of the trade and add or lighten then it should be ok.

Also Im assuming IB allows the 3/1 pairs trade to be placed as one trade.

My Trading hasnt got to this level yet but its interesting as there may be more Volatile pairs that could offer the swings to jump in and out.