It seems to me that judging from LP's attitude to this whole promotion that they will NOT post the miles if they can possibly avoid it. I do not want to give them any excuse not to post my miles. What is a $200 saving by booking multiple segments on one ticket when you risk losing 500,000 miles or a million miles - in relative terms, it's nominal. Be safe and book each segment separately, IMHO.
To any under 24s out there: a very good way of getting the partner segments is to buy a US Airways Youth Flight Pak on the US Shuttle. It's about $230 for four coupons. Yes - I know it's more expensive than just 2 round-trips, but it's flexible. You just tip up when you want to at off-peak times. They do qualify for ff credit. I don't know about US, but on the DL Shuttle, you can stand-by at other times. Given that they're in direct competition with each other, this will probably be the same on US.
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Cheers.
Leo.