Yes I have (it took a lot of time and tries !). As far as I understand, the problem comes from a bug in the version of Asterisk used in Elastix 4. When the gateway tries to register, asterisk uses the trunk name instead of the username, and the registration fails.
You have two options : either use the same name for the trunk name and the username, or register in the other direction (Asterisk registers to the gateway). Here is my configuration in Elastix :
Trunk name : Numeris 3
Peer details
host=192.168.0.182
username=Numeris3 (should be the same as trunk name)
secret=abc123456
type=peer
nat=yes
User context : ip800-trunk (put what you want here)
User details
secret=abc123456
type=user
context=from-trunk