What year is your slingshot..... my 2015 schematic shows the top fuse is for the engine circuit 40 amps. Middle fuse 40 amp. Bottom fuse 50 amp. The melting is on the back of the J Case.
Check your schematic.
mine is a 2016 - top fuse is 50 amp and clearly marked main chassis on the cover center fuse is also 50 amp and is ABS motor and the bottom is 40 amp and is engine - here just for you I opened it up and took a picture - - also in the PDF that Rab posted showing the inspection picture and the fix the melting the melting could be seen on front down where the contacts come through as well as on the back