If you do want to use IGBTs then I think you're best to follow the advice in #2 - they should behave just like MOSFETs in this application.
Could you clarify, though, that you are talking about a linear reglator not a swiching buck converter? Just to make sure we're all on the same page.
If you are talking about a linear design then the limit on the current capability of the regulator is likely to be set by how well you can get heat away from the pass devices (IGBT, MOS, BJT etc), so I'm not sure that an IGBT really offers much advantage. You might be able to get several NPN BJTs for the price of a big IGBT, and I think that it might prove rather easier to design a good regulator using BJTs.
Don't let me put you off IGBTs if that's what you want to do, and if it's a switching converter then ignore what I've just said.