You can machine the whole piece from one solid block of PA.
It would be very very helpfull if you can acces a lathe, router, stationary cutting tools, drill stand, stationary belt grinder.

First shape the block to fit the inside of the mast, leaving a rim, then process the end part into a cone shape with a hole inside.

Not too much work, but this is just a fairy tale untill somebody helps with some numbers. GFPA6.6 is used a replacement material for steel to make pump housings and other industrial parts where steel can't be used due to corroding environments. It should be strong.