I would steer clear of S/S in this application. As was mentioned the grade of S/S is important.
In years gone by some ocean racing yachts had S/S fins and t/plates with a lead bulb. After a period of time with the flexing of the fin the weld joints started to show cracks, and in a few cases the keel fin breaking.
I am no expert but why change from what has worked before ,good old steel.
Jeff