I have Eddys, Quattros and Go Sports (the boot version, not the travel version). Not sure what your problem was in the current but my Go Sports are every bit an equal of the Eddys and are lighter as well. The Quattros produce more speed in a flutter but do not pack well and are a bit heavier than the Eddy and especially the Go Sports. But for current the Quattro is the superior fin by some margin. I can do all of the manuvers and kicks with any one of the three. The Eddy size L and the Go Sport size L are about the same dimensions overall. The Go Sport is more comfortable as well. Frankly, I like the Go Sport better than the Eddy but would agree the heavier Eddy is a bit more robust and has a spring strap vs a bungee cord for the Go Sport. I too have Slipsteams size XL and would also agree they are the stiffest and most powerful and least comfortable, best for frog, worst for flutter.
Go Sports driving me forward against stiff current in Cozumel, no problem (photo by LH):
James