I'd say keep them off considering it will help you cut properly, but I have never ridden an Ibex so I guess it's more up to how that board rides and how loose it is in general.
put them on if you like it locked in take them off if you dont..... if your just startin i would say put them on that way its not slick for you.... i ride an 08 ibex 144 and keep them on... but i cant stand a lose board...
I have my fins on right now and it is just slightly too locked for me, will probably step them down a size soon. I would suggest keeping them on until you feel they limit you in some areas. By that time you will also know if you want to take them right off or if you just want smaller ones.