This might not work because of your daughter's height... but I used a double from Orlando Stroller Rental - the city mini for a tall 6 year old that was maybe 55 pounds and a small 14 month old and it pushed beautifully with the uneven weight or when just the little one was in it. The owner there was really helpful when I emailed with questions about my girls sizes saying what would/wouldn't work. They also have the liberty special needs pushchair so maybe you could call/email and ask her opinion.