downwards load at mast base, how much is it?

[bikedaft]

6 tonne hustler 35, keel stepped aluminium mast. some corrosion at base, so cut off 1", put base plate back in mast, and make up a 1"pad to put under mast. how much load will it take? i have heard of a rule of thumb of the same weight as the boat ie 6 tonnes, if so should i make sure it can take 12 tonnes, etc?

also what to make pad of? hardwood, s/s, or aluminium??

thanks