For an upcoming trip in Y, I have booked the following:

> LHR-BOS: 33H and 33J on a 747 (70J)
> BOS-LHR (day flight): 39A and 39B (on a 777 4 Class)

Are these reasonable choices (most seats are available to choose from still)?

Addditionally, I am a Oneworld Sapphire. Do any additional seating options open up at T-72 hours (eg exit row seats, bassinet position seats etc)?