Radian in 2009 Sonata

Update, I got it rear facing, so I know that will work once I get my daughter some new car seats BUT when I install the Radian forward facing with the seatbelt, I find it moves at the top. At the base, it definitely moves less than 1". At the top, with the tether strap as tight as I can get it, the top of the seat does move forward a little. Is this just because the tether straps are attached fairly low on the Radian body?
I can get my marathon installed wickedly tight so the Radian being able to move is strange for me.


*******

I think I am in big trouble. We should have bought the car seat before the car.

We just bought an 09 Hyundai Sonata. Bought a Radian last night and tried to install it rear facing in the centre back row with the seat belt. The seatbelt does not lock therefore I need to use the locking clip. The "female" end of the seat belt buckle is long. So when I buckle the seat belt together, the lap/shoulder belt ends up half way under the seat (which makes getting the locking clip on almost impossible... unless someone has a trick for me). Is there anything I can do to make it so the female end of the seat belt is shorter? I keep hearing about twisting but I'm not 100% sure I understand what that means...

I got it tied up but seemed somewhat loose. Probably more than the 1" side to side. I'm going to try it again today, in the daylight and I'll see if that makes a difference.

Right now I have two kids.
My daughter is almost 3, 37 inches tall, 30 lbs forward facing I hope to get her a forward to booster seat to put in the car beside the Radian but I want to figure out the Radian before attempting to puzzle a seat beside it. Any opinions on what I should get?

My son is 10 months. 21 lbs 29.5" tall and I will keep him extended rear facing.

I need to put a seat in the middle and one on the side... I have to keep one of the outside seats empty for now.


I am also open to other car seat configurations...

I did check the successful 3 across and a radian in the centre worked for someone else... I just don't know what I am doing wrong.

To make the female end shorter you can twist it up to three full rotations. Hyundais have long female stalks. I just put my son's Radian in my parents Elantra yesterday and I think I twisted it one full rotation. Also your belts absolutely do lock (unless it's broken in which case you'll need to have it repaired before using it). To lock it, pull it all the way out very slowly and as you let it back in, you'll hear a ratching noise. That means the belt is locked.

Thank you.
That will teach me to try installing a car seat at 11pm in the dark.

You are right, it does tighten on its own. I guess I hadn't pulled the seat belt out far enough to engage the ratcheting last night. That was way easier. I did also have to twist the female stalk once.

Now that I know I can install it, I have to take it out. My son in still in his infant seat, so my daughter will be using the Radian until we can buy her a new car seat for each of our vehicles.

I guess I really need to re-read the car's owner's manual too. I skimmed though it at the dealership before buying and haven't looked at it since. To be fair, I've only been in the front seat of the vehicle once, when I test drove it and haven't actually been back in the car, when running, since. DH drove it home from the dealership.