Slide(new board)

I have bought my own board now with Obrien bindings but when i try to slide it doesnt go smooth at all and i cant keep it up.
I have a blindside board(assasin)
http://www.wakeworld.com/boardguide/getboard4.asp?ProductID=1848
I think the fins are too big, i have standard 1.5 inch fins on it 4 of them I used to rent a Cwb tattoo board with no fins at all and i could slide for a long way but now I cant any suggestions?
Maybe smallers fins?Or take them of?
And what effects will that have?

What doesn't go smoothly exactly? Are you not able to hold the slide once you get it going or are you having trouble releasing the fins to go into the slide? With big fins, it is harder to get the board to release, but once you're sideways with proper weight distribution (and handle positioning) you should be able to hold on. I used to do slides with HUGE fins (2.8) on my 99 shifty, so even tough big fins make it harder, everything is possible with proper technique.

For some reason, I always found reverse sideslides (with you back facing the boat) were easier to hold for a long time, you might want to give that a try. As for removing your fins, it will definitely make all surface tricks easier, and most people say it will help you work on your edging technique, but at some point you'll have to put them back, I don't think this board is meant to be rode finless.

Thanks for your answer I ride Cable bytheway.
Its good to know it can be done with big fins knowing this its probably the transfer from a finless board to one with 4 fins.
I dont have trouble getting into the slide I just go heelside and than into a slide but when im standing sideways it feels like every little wave is bumping against the fins could be just my technique I just started sliding.
But ok thanks for your answer