The value of a prolate primary lies apparently in the fact that a MIRV warhead is limited by the diameter of the primary — if a prolate primary can be made to work properly, then the MIRV warhead can be made considerably smaller yet still deliver a high-yield explosion — a W88 warhead manages to yield up 475 kt with a physics package 68.9 in (1.75 m) long, with a maximum diameter of 21.8 in (0.55 m), and weighing probably less than 800 lb (360 kg).
Other references indicate a low end of 350 KT and high end (theoretical) of about 4.8 MT.
Heckava flash bulb.
MIRV weapon calls for between five to twenty per package, so they are made smaller to fit. Single war head package, say on the old Titan rocket or Minute Man could be made even larger than 45MT. Theoretically almost not limit dependent on delivery system. Much under .3MT and you lose most of the fusion effect and it becomes a fissile (Atom) bomb. 2 to 5 percent now is fission, 95 to 98 percent fusion. That’s why bigger is cleaner, air burst with size, ground burst absorbs neutrons from the fission side. Down wind on the old bombs, really nasty.