Stainless has less tensile strength than convential steel bolts. i would think twice about using them in sucha high stress area.
titanium alloy bolts are also a risk unless you go for high tensile grades of tianium fasteners. Pro-bolt are OK for cosmetic applications but appear too soft for high stress areas. If you cab get high grade Ti alloy fasteners then these are an ideal choice (I recommend Poggipolini - although the British contact is mercurial! i.e. promises to get stuff and then goes off the radar!). JHP usually have a selection of Poggipolini. Don't skimp on cost for usch an important application.