Hi there, well thanks, hope you too and stay healthy in these tricky times, soon we'll be back on the water hopefully!
Did you mean a FreeWave 115? as I started answering the Allwave question which is a SUP, but we don't have it in SUP. So assuming you have the FreeWave 115, I would say try it first with the single fin, if you feel you want to get tighter turns/more manoeuvres - then go for a 21/22 centre fin and 12cm side fins, we use the MFC TF fins, they work really well as plenty of lift and drive but good turning. If you go for some K4 fins, get 1-2cm bigger on the centre fin and try to get side fins in 12cm with zero angle, as the boxes already have a slight toe/angle? good luck!