Slat length for bench with two heavy iron sides
What can the span be for an outdoor bench with two heavy architectural sides and an iron support band/brace to go between them for each of the following woods:
I’d also be grateful for advice on each of these woods, how thick the staves should be (the iron sides have bolt holes that determine how many staves there can be).
Is there any other wood I should consider using? My lumber yard recommended against cypress and cedar and I don’t want to use pressure treated.
Finally, what type of bolts should I use to secure the staves to the iron sides? Stainless steel or galvanized?
My thanks in advance for your help.