My clowns stayed in the farthest corner for a good week or two before exploring the rest of the tank. Even during feeding time, they would grab a mouthful from the opposite corner of the tank, and then dart back to their corner, finish it and do the same thing over again! Now, they're happily swimming all over the tank.
Regarding hosting, they both hosted my heater for the longest time ... then they moved onto my Xenias ... now one of them is hosting my torch coral, and boy is she protective of it or what ... does not let the other little guy come anywhere close to it! The other clown is now sort of hosting the frogspawn in the tank, but at night, he back to the heater!
So, there's no telling what they'll host ... like some others pointed out, don't get a particular coral/nem etc with the hope that they will host it, cos there really is no guarantee at all.
Cheers!
Yash