The copper tube inside the hose "nipple" was unsuccessful, and perhaps at least partly my fault. My first repair attempt failed because I used a c clamp to hold the crack shut while the epoxy dried, and later found the epoxy only had a 200 degree rating. Attempt 2 used JB weld on the crack WITHOUT the c-clamp. A small leak remained, so I tried to install an inner copper 1" coupling which IS a perfectly tight fit inside the plastic. It wouldn't enter completely, and when I tapped it with a light plastic hammer, the nipple cracked in another place. Seems that the JB weld epoxy had oozed into the first crack making the hole slightly smaller and the copper pipe was butting up against the hardened epoxy. So I slopped JB all over the nipple and into the new crack, put the copper tube in as far as it would go, and waited for it all to dry. I then reconnected the hose and fired her up. No luck. Still leaked. When I tried to tighten the hose clamp further, there was too much give and pulling it apart, the nipple had basically disintegrated.....I now have a replacement radiator for $100 from the bone yard.
In talking to my mechanic, he related that when the MB's "environmentally friendly" plastic and aluminum radiator eventually fatigues, even with the tube in place, odds would be high the plastic would crumble anyway.
If I were ever to do it again, I would take extreme care to insert the copper sleeve gently. And, I would take the extra step of wrapping a piece of epoxy soaked body repair fiberglass cloth around the plastic nipple to re-enforce the brittle plastic.