Cook whole squash in boiling salted water till just tender, .15 to 20 minutes.
Cut a small slice from stem end of each squash.
Scoop out pulp, leaving 1/2-inch shell.
Finely chop pulp; set aside.
Sprinkle shells with salt.
Cook bacon till crisp.
Drain, reserving 2 tablespoons drippings.
Crumble bacon; set aside.
Cook onion in reserved drippings till tender.
Stir in crumbs, milk, and squash pulp.
Fill shells; top .with bacon.
Bake, covered, in 12x7 1/2x2-inch baking dish at 350Â° for 30 to 35 minutes.