If you're pushing 10A @ 1.2V the only sensible approach is a buck regulator.
Otherwise your dumping 450W+ into the heatsinks
I'm actually playing with a MPPT circuit at the moment, and I keep getting the supply going into thermal shutdown at a lowly 2A (40V capable unit).
I'd Love a switcher right now
(other than the one I'm working upon within the MPPT)