As a carseat technician, this is a subject that is very near and dear to my heart.
First things first, please watch this video, and then seriously reconsider turning your baby around at 1 year old. (This is for any mama considering turning their baby around ASAP, not specifically H.)
http://youtube.com/watch?v=psmUWg7QrC8 - the crash test clips in this video are enough to scare me out of turning a little one forward facing so early.
I cannot stress this enough, PLEASE KEEP YOUR BABY REAR FACING AS LONG AS HUMANLY POSSIBLE!
Most convertible carseats on the market rearface to 33 or 35lbs, and you should take advantage of that weight limit and keep your baby rear facing till he hits that weight limit!
12 months and 20lbs is the BARE MINIMUM that you can turn them around, but just because it is a choice, doesn't mean it is a safe choice! In many other countries children are rear facing till they are 4 or 5 years old, and the injury statistics over there are shockingly lower than they are here in the US.
I have a 2 year old niece who is 27lbs and will not be turned around until she hits the 35lb weight limit of her seat.
Here are a couple links for you!
http://www.car-safety.org/rearface.html
http://www.childrestraintsafety.com/rear-facing.html
http://www.cpsafety.com/articles/StayRearFacing.aspx
http://youtube.com/watch?v=kRP7ynNI8mI - another video about rear facing
Also know that it doesn't matter if their "legs are crunched" while they are rear facing, your child will be fine, crunched legs are NOT an issue nor a reason to turn them around to forward facing. If you were ever to be in a crash, a broken leg could be fixed if your child were to get hurt (and really there aren't very many reports of "broken legs" due to extended rear facing) but a small 20lb child cannot have their snapped spinal cord repaired because they were forward facing.
To anyone who reads this, I am more than willing to help parents with anything car seat related (installations, shopping for a new seat, etc etc) just email me!!!