Fins will only help a boat with a faster hull, ie. a surf or freestyle surf kayak. Only in some specialised aerial tricks will small fins be of any help (that's also debatable) and 99% of paddlers aren't doing those moves anyway. Remember, you will be able to ride waves and have fun spinning around and doing some blunts and what not but you will not have the hull speed for bottom turns and cutbacks. For that you need a more specialised kayak like the Fluid Element (not a true surf kayak and branded as a freestyle surf kayak) or a full on surf kayak like something from Watertech, Mega etc. to be able to really ride a wave. Of course, these boats cannot be used on rivers so unless you are going to buy more than 1 boat, stick with something like the Spice so you can enjoy the rivers too. So to answer your question, don't waste your time with fins on the Spice. That would also smack it's resale value down to the ground in my opinion.