Thanks for the good advice guys. About to dive in and will let you know how it goes...
It looks like the Honda bolt has a 6mm head, and the automotive bolt I sourced had an 8mm head, so I guess I ground it down by about 2mm.I've taken those bolts out a few times and never paid much attention to the height of the hex head part so now I'm curious, what size is the bolt, and what's the difference in head measurement between the std. bolt and the Honda version?