Magnifica is one of the easiest anemone to keep from wandering. Most of the host anemones require stable condition with great water condition to be happy. They will move if unhappy. It is a lot easier for me to keep Magnifica from moving in compare to BTA.
For Magnifica, if you provide them with adequate (very bright) light and current, Good and stable water condition they will not move. Even with sub optimal condition, it you put them on an island of LR so that in order to leave the island, they have to move down first they will likely not move because moving down will result in lower light and lower current.
However, if condition is too bad for them to tolerate, they just release and flow with the current.
My tank is mostly SPS with anemones. I don't have much room in my 320 for SPS, but what I have are doing great.