I KNOW my BX23s lifted the rear set of duals (2 tires,rims and brake assy) from a dumptruck one day. OK, it was struggle and only about 4" off the ground but it did carry them,up a bloody long steep grade too !
according to the manual, max lift is 700#, take off 120 for the bucket, another 120(?) for the SSQA frame makes for a 460# payload AT THE FRAME, you lose a lot at the front tip of the bucket.From memory, it couldn't carry 5 'big' patio stones ( 80# each), laying flat BUT no problem if vertical,back against the SSQA frame.
yes, it would be nice to haul more BUT front tires aren't rated for much !!