I believe the Foil Works base plate may actually be slightly thinner than the Slingy plate. If i can find my old calipers i can take a measurement. The Infinity slid on perfectly easily on the Foil Works fuse. Once i slid it on i had to back out the fuselage a bit less than a centimeter to align the bolts if that makes sense.
Here is a comparison of slingshot mast to others, thats why I was asking.
I think sanding the fuse to make a wing fit is somewhat troubling for one that means your taking off the protective paint coating over the aluminum, which may lead to corrosion over time.
I don't think backing the fuse off on yours to get it to line up is a big deal but I don't think I know the mechanics of the fuse connection well enough so say whether it's ok or not.
The masts are the same between Slingshot and Foil Works. I know this because i have a 60cm Slingshot mast i use with my Foil Works base plate for shallow water kitefoiling. Personally i wouldn't hesitate at all to mix and match between Foil Works im fact i would highly recommend it to anyone trying to save a few bucks in this incredibly overpriced sport.