The ClickTight convertibles are usually pretty compact, so playing with what you have may give you a bit more space. You could install it without the ARB, try it in the center if that space is available, and make sure the recline is as upright as possible. If you've tried all that and it still isn't working, we can make other suggestions.
The most compact seats I have used personally were the Graco 4Ever and the Cosco Scenera Next. The 4Ever requires a deep recline FF for kids under 40 pounds, which can be annoying or impossible in some vehicles, but there are similar models that don't have that requirement. The Next is a great budget and travel seat, but judging by the seat you have now, you probably wouldn't like it as an everyday seat.
There are others that could work for you, let us know if playing with the Advocate helps and we can give you more suggestions if you need them!