I just got the Motorola, case from heck, to work. I used foam double sided mounting tape. The kind used to hang light pictures on the wall without using nails.
2 x ½" x 1" strips put into each groove. The tape did not stick well to the textured case. I heated it a shot from a gas lighter (biggest trick in this hack). Zoom's metal case is highly polished and touches the strips in a line. It does not get glue on it and is not sticky removed from the groove.
I'm sure that the strips will need replacement but it takes about 1 minute and I got roll of tape from a $1 store for a couple of feet or tape.
xxxxxxxxxx Rear ^
xxxxxxxxxx Front v
Try to get the forward edge of tape to roll up the groove on the forward side but not high enough to touch the glass when the case is closed.