Right third time lucky.
I tried the gel case that has no front, still use that, it has grown on me, see my review.
I am returning the Terrapin.
This neoprene case is good, it is not a SE product, but, it fully covers the phone, is Velcro-ed shut, so virtually zero chance of phone getting out, is soft and protective, just don't sit on it! I presume being neoprene will offer a little protection from the elements, and most importantly, the Arc fits perfectly.
Unless someone finds a better case for the Arc, this is the one.