Hey Tom, I'm guessing you have the stronger WVX kite
construction version. I thought that one came with better fins? Maybe not good enough...
Funny thing is I have the 5'0 wake version and love it. I didn't have any issues with the plastic fins but enough people told me they sucked that I bought some high quality fiber fins and love them. Have hit them tons of times and other than some scratches, no breaks. (never did a fin to fin comparison, but no complaints with the upgrade).
I just bought the 4'6" wakeskate version you mentioned. It's awesome as well. (I bought it for travel since it easily fits in a Golf bag.) I rode it for the first time today and the fins hummed like the rudder blades on a catamaran! Funny. Didn't seem to affect the ride. My 5'0 never did that nor did the other two pickles I demo'd so it must be board specific or fin installation. Here is a video on how to fit the FCS fins
to a board, which may help. I'm sure the plastic fin doesn't help with the vibration, but the hum doesn't seem to occur on all setups. ?
If you're comfortable on your 5'0, next time try it with the rear fins off. When you want it to track solid keep your foot over the fins, but move your foot back and it's loose and fun. Rides more like a skim than a surf board and makes for quick little turns on small waves. I haven't tried it yet with the rear fins on and the front fins off. Their website says it is more of a "longboard feel" although I'm not sure what that means.
Anyway, fun board. Glad to hear you like yours also.