I have seen many "tests" done on tractors and being tested for inclines. HOWEVER all of these were tests done with a machine sitting on a platform and the platform tilted on the side.
WHEN the machine is moving, this changes everything!!! THE higher the center of gravity the worse it will be! One of the biggest advantages of BX over the B series, is the fact it is "lower" to the ground and has a lower center of gravity.
Properly weighted - your machine will ascend and descend a hill @ 20+ degrees, however, as others said - going sideways is never a good idea!