It is installed in the center with the seatbelt.
I didn't try to install it. I was in the store with an overtired girl
But my husband said it was on 3 and that it was hard to get the bubble level & get the seat in. It fit on the passenger side but not comfortably.
We had this exact same experience! I nearly started crying because I had done a ton of research and knew I wanted the Nextfit and I knew that it was one of our few options and it didn't fit! Like you, we weren't installing it, just putting it on the seat and shoving it into position. We tried it on recline 3 and the bubble level wasn't right. We tried it on recline 2 and it wouldn't fit. We were about to take it back in to the store and resign ourselves to
buying another vehicle when I said to my husband, "what if we just try tightening it in?" So we did and we found that it gained us a lot of space. Like -- enough space that on recline two (where we couldn't even get in to the front seat with the car seat uninstalled because there wasn't enough room up front), my husband got in the front (this was on the driver's side) and said, "oh yeah! I think we moved this seat all the way back to where I usually have it!"
You are welcome to pursue other options, but I would strongly recommend going back and trying the Nextfit again. It takes maybe 2 minutes to install it (with lower anchors) and makes a big difference. Could be exactly the amount of difference you need.
ETA: it will take you a little longer to install it in the center with the seatbelt than outboard with the LATCH. But I'd still go back and try it!
Edited again to add: I may have misread your post because I got too excited to share my story -- just noticed that you said you didn't install it because you were in the store -- not that your husband didn't install it...did your husband install the seat when he tried? Also, I could be totally off on this, but I wonder whether you can get the Nextfit tighter against the back of the vehicle seat with LATCH than with the seatbelt? I am sure you can get a secure install with either, but with LATCH it might be easier to ratchet it tightly so that it's compressed against the seat back more and gives you more space in front. Just an idea, if you were willing to try an outboard install instead of center.