The alpha omega elite, depending on the version, might have a removable base. It's usually easier to install without the base on, so you take it off. The other thing is, you usually need pool noodles to istall it rearfacing,to get the correct recline, even for an older child. i don't in my car, but that's fairly unusual. Once you gae the poll noodles, it's actually a fairly straitforward install. It is on the bigger side, but it's not huge. And, you can always make it more uprigfht if you have to to save room, as long as oyu dont go under 30 degrees.
A specific descriptoin of what exactly the problem is, as well as preserably, pictures of the issue, will really help us help you better. Also, a child has to be a minimum of 1 year old, 22 pounds and 34 inches tall to rearface in that seat, if any criteria are not met, you cant use the seat Forwardfacing. And thats a bare minimum legal standard, we know that stayng rearfacing for at least 2 years is the better choice, and up to 4 years has proven safety benefits.