When I got my Giant Halfway I read all reviews available online (not a lot, mabe 3 or 4) and one of he MAJOR complaints was the chain coming out frequently.

When I went to the local bike dealer and mentioned that, more than one bike tech mentioned that 99% of the chain problems they deal with on a regular basis has to do with poorly assembled bikes. Rear wheel assembly is a deep, intense mix or art, science and experience that almost no difference between perfection and far-from-good-enough.

in other words, most likely you problem may not be the lack of an "inner guard", unless you are the 1% with a defective product. Just take your bike to a good bike store, give them 10 bucks or so and ask for a rear wheel check-up.

It worked for me. Halfways have a history of chain problems, I NEVER had mine out (not even once).

Rafael