US Airways Dividend Miles (Pre-FlightFund Merger) - Booking Award: Hold 1, Try to Book a Better One?

I am trying to book award travel using US Air miles to fly United to Hawaii next year. I can travel in July (1st choice) or June (2nd choice). I currently have the outbound leg in June booked, waiting for 331 days out to book the return.

Here's my question: I don't want to give up the June booking unless I have both legs of the July booking in place. Can I leave an unticketed but complete June reservation in place, then try to create a second booking on a new record locator for July (book first leg, then wait 10 days and book return) without jeopardizing the June reservation?

I only have enough mileage points in my account for one set of tickets. When booking one leg at a time, at what point in the reservation process do they actually look at the number of miles available? Will two separate reservations get rejected by the computer for insufficient miles, even if the miles are not deducted until the tickets are issued? And if I have to ticket the June reservation, will they also reject any subsequent attempt to book and hold one leg at a time due to insufficient miles?

Thanks for any help you can provide.

As far as I know, you can hold them both, and they shouldn't take the miles out of your account until you ticket it. I've done this before, and its' worked for me.