Just posting to say, EV's at level 50 are not entirely the same as EV's at level 100. If you have an even IV (30 Speed/SpA for HP-Fire, for example), you should only place 248 EV's (or any other multiple of 8) into that stat, instead of a multiple of 4 like at 100. 248 EV's gives the same stat while allowing you to place 4 EV's into another stat, giving a free stat point.
For example, for a level 50 HP-Fire 70 Latios in GBU, the EV-spread should look like 4Def/248SpA/4SpDef/248Spe, with the 4 extra EV's placed in either Defense, or HP (provided the IV is odd).