I have the hex string set up on my SRX in this fashion for a BlueSocket depoyment as well, but it doesn't seem to be working. The option 43 information is not appearing on the access point. I have an EX4550 set up similarly, and that seems to work fine.
[edit routing-instances EDIA-WIFI access address-assignment pool OTT family inet dhcp-attributes]
name-server {
72.240.13.6;
72.240.13.5;
72.240.13.7;
}
router {
192.168.250.1;
}
option 43 hex-string 36382e36342e33372e32342c4636392e322e3231322e313034;