Can I obtain a double entry L-visa even if i only plan on entering PRC once?

I am planning on entering PRC as part of a round-the-world trip in December. However I will be in the USA from September to December so cannot apply for a single entry L before I go (In August) as the 3 month validity period will expire before I want to enter in December.
(I cannot apply for it whilst in the USA as they will not allow people on a B1 visa to apply)

I was hoping to apply for a double entry L in August (while i'm still in the UK), as this would be valid for 6 months, however I will only have airline tickets and a hotel reservation for one entry. Will this be a problem?

If you have any other advice on how I can obtain it for my trip it would be greatly appreciated!

Thanks