Yep, stainless is not stronger, but I used in in some places as it is stronger enough and since I often cut the bolts to the proper length, I did not want to worry about unsightly rust at the cuts where there would be no zinc plate on a regular bolt. Not a strength issue...but I can be a tad compulsive that way.
That being said, I know some have had sucess with the original hardware, but even if it is good enough, it is obviously softer than grade 3, let alone the grade 5 (or metric equivalent) that I use most of the time.
I replaced the mounting tray bolts with decent hardware (Grubee 4 stroke), but the real problem I had was with the mounting bolts for the sprocket...which appeared to be the approximate hardness of slightly chilled cream cheese.
In the end though, if you want a gas and go experience, this ain't the hobby for ya. If you want to take the rough components, make something to your vision, and improve everything along the way- welcome to the club.