If you sleep cold or are over 6' tall a 3/4 UQ might be a struggle to get into a comfortable "Warm & Toasty" position to sleep in.
I would suggest a full length UQ -- contact Stromcrow (Adam) @ HG http://www.hammockgear.com for your best option. I have have both the Winter Yetti from WBO which is a GREAT UQ but too short for me and the full length 0° Incubator from HG. The 8 yr old inherited the Yetti - :-) The wife and I both have the full length Incubators and are "Toasty Warm". I was out this past week in 2 layers of cloths and just the TQ & UQ from HG it got down to 25° and again "TW"
I did speak to Brandon @ WBO last year about a full length UQ and a short version BB for kids but he's jammed with what he has and wasn't (at that time) planning on adding the full length Yetti or a kids version of the BB to his offerings ......
LOVE my WBBB 1.7 we have 2 of them and if Brandon made a kid version it would be 3.
Our 8 Yr old has the scout from HH.
Good Luck & Happy Hanging!!!!