Chromo birfs are much stronger then stock.  Unless your running 37" tires and fully locked with hydro steering I dont think your gonna break it.  Also get a set of a spare marfield or long isnt gonna happen since the longfields are life time warrantied and the marfields are warrantied for 2 years or more and dont break really.

On 36s currently, locked in the front, and HA coming soon.  I'm just not convinced that this mystery composition birf is up to par.  And I agree, it's a long shot hoping for a single birf.  I'd take a pair if I could find someone upgrading to 30s.

Or you could just get longs and be done with it.

If I can't find something in the near future, that's probably the route I'll go.  Nothing wrong with waiting to find a good deal though.