Bolting the floor frame down

Should I use grade 5 bolts to bolt my floor down to the trailer, or would simple SS bolts and nuts be ok? I cant find any mention of it anywhere to use grade 5, but I want it done right. Thanks
or t n ttt for short (tnttt.com)
https://www.tnttt.com/
Ira wrote:Actually, Finn, most people do the wooden floor frame so it's LESS than the trailer frame dimensions. This way, when you put your walls up, they sit on the trailer rails themselves--not on your wood frame. Also figure in your intended skin material thickness to make it PERFECTLY flush with the edge of the trailer frame.
This is a really correct way of doing it--which means I didn't do it this way. My sides and skin hang over.