@350# you are past the max on cane creek Thudbusters ... but you might go with a sprung Brooks
Again, But .. don't expect it to be perfect right away, you need to get used to each other
Otherwise maybe a 29er + bike with wide low PSI set of comfortable tires ..
Rinsten is a U shaped spring tempered steel wire .. maybe a local artisan blacksmith can make something heavier capacity.. perhaps incorporate some auto engine valve springs in it..
Spring tempering is a heat treatment procedure..
You already have a reasonably comfortable fitting bike , as it is, now?
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Last edited by fietsbob; 06-05-19 at 11:52 AM.