Stainless not ideal down there, Bronze is perfect and strong and appears to have some vibration damping properties compared with the carbon launch ones I have experienced, the weight is negligible and down where you want it , unfortunately the two foundries that understood the requirements (both in Porana road are both closed).
Dont use HDPE for a cutless bearing or you will have to machine it half worn out to allow for the water swell, use a brass shell / rubber cutless or Vesconite both of which have decades and decades of history in that application.