@LO ....Long ago (2007-08) there was marketing puff about 6 internal AMRAAM. The fact that it's gone away suggests that it was found to be impractical.
I suppose this is why LM wants/needs to develop the Cuda missile, although one of its own test pilots is calling for a longer range AIM-120 / AARAM class missile for the F-35. Hard to imagine a smaller missile having the range necessary for the JSF - JPO "first to see / first to kill" meme. Likewise, it's unlikely that you could cram more than four longer ranged missile into the internal bays - maybe only two? I think the mock ups of the Meteor load out only shows one per bay, but four are planned.