I'm afraid I cannot help for HB-72.
But for HB-47 (if you use 50/1.8G and not 1.4G) and HB-38, you can screw in the step-down rings to use lens caps of smaller size, which enables you to put on and off the caps much easier. I use a 58-52mm step-down ring on my 50/1.8G. I don't have the Micro 105 VR, but a 62-58 ring should work. For the 50/1.4G, the ring might cause vignetting because of the larger front element.
With the hood put in the shooting orientation, I would think the hoods would prevent the caps to fall off in the bag.