Bays themselves seem pretty much the same, dimension wise. doors have been changed, as well as some internal support structure. And possibly the rear part of the bay now has a slant surface (aerodynamic reasons?), if it didn't have it before.
Issue is still size of missiles. Each bay seems to be around 92 cm wide at its narrowest (hinge) and around 96 cm wide for most of the bay length.
Missile fin cross section seems to be around 37 cm. Now even if the bay figures are not precise, and bay is a bit wider, then missile is also wider as ratio of 92/96 to 37 is pretty precise from the available image.
Amraam is a narrower missile, with fin cross section being 316 mm. F-22's bay is around 95 cm wide at its widest. that is 32 to 95 ratio. Evidently, with 3 amraams inside a bay, and body diameter of 18 cm, it's arrangement is something like this:
3 cm space from bay wall to missile fin or 10 cm from bay wall to missile body. 18 cm for missile body. 10 cm from missile body to body of missile next to it (allowing for 3 cm of space between fins). 18 cm for the middle missile. another 10 cm for fins interlaping, another 18 cm for the third missile and another 10 cm from the missile body to the opposite wall. total of 94 cm.
Using similar clearances, if one wanted to stick 3 pl-12/15 missiles in the j20 bay we'd have: 3 cm of clearance from the wall to first missile, total of 9 cm from the wall to the missile body. 20 cm for missile body. 9 cm between two missile bodies (6 per fin set plus 3 for clearance between it and neighbouring missile body), then another 20 cm for middle missile, another 9 cm between two missiles, another 20 cm for third missile and another 9 cm from the third missile to bay wall. total of 96 cm.
I guess it is possible, though not guaranteed. On the other hand, if air superiority is main role of j-20, then the design would very much exploit the maximum and bays would be designed around air to air missiles primarely. In such a case it would be wasteful to have bays this wide if they're to carry only two missiles.
Of course, image measurement could be off by a few cm, so all this is far from conclusive.
