No issue In configuring LUA for SEP 12.1. I myself has configure 8 LUAs in SEP 12.1 Environement. No worry it will work fine.
These Articles will Help you Understanding and Configuring LUA.
Best Practices for LiveUpdate Administrator (LUA) 2.x
http://www.symantec.com/business/support/index?page=content&id=TECH93409&actp=search&viewlocale=en_US&searchid=1355113883050
Installing and Configuring LiveUpdate Administrator (LUA)
http://www.symantec.com/business/support/index?page=content&id=TECH102701&actp=search&viewlocale=en_US&searchid=1355113883050