The MiG 1.44 demonstrator apparently didn't have a bay, just a recessed area under the central fuselage. It looked like it could potentially have enough space to mount 4 R-77 Adder missiles. Maybe MiG hoped to eventually add an internal bay in that space.
http://www.aircraftresourcecenter.com/rh/ssi/image_popup.php?id=47899
According to drawings on Paralay's website (http://paralay.net/mfi.html) of the production MFI 1.42 design, it would also not have had a bay but conformal missile carriage points:
http://paralay.net/142/3d.jpg