hmmm i haven't done it before, but if it were me i'd be getting her her own seat... an hour is one thing, but 7 hours of holding her on your lap etc, well i know with my dd there is just no way she would go for it, she'd have a fit.

i'd also be timing it for when she is awake, cos i know with mine, if it was night time and she was ready to have a sleep, but wouldn't/couldn't, it would make things ALOT harder due to her being cranky and overtired, IYKWIM, whereas during the day she is generally happy and okay...

anyhoo good luck, (brave) people do it all the time so i'm sure you'll be fine!!