I use 14g fine silver for the post I embed in the top attachment, and thread it through a hole I drill in an Argentium band. This is a variation of a Kate McKinnon technique, and I am eternally grateful for her exhaustive work with rings. The reason I also place some solder where the attachment meets the top of the ring band is merely for additional strength. It acts more like a glue or tape and is not strong enough on it's own to hold on the top, it just keeps the top more stable if it gets knocked. Notice I file the bottom of the attachment and the top of the band so that I have a larger area of contact, and less ability to rock. It's the rocking that will pop the top off. It will eventually stretch the fine silver post.
The fine silver post solders beautifully to the underside of the ring band. This will hold, but, again, it's the top that will provide any trouble.
I am NOT in favour of soldering metal clay to silver without additional reinforcements, such as embedding wires. Yes, it can be done, as in the step of soldering the attachment to the band, but this is only a "piece of tape" measure. There are many instructors who will tell you it's fine, and will hold, but, remember, I make stuff just to tear it appart. Metal clay soldered to silver is EASY to snap off. Try it sometimes.
Oooops, that leads me to another thing. Please make a throw away piece whenever you are trying a new tecnique in order to try to rip it apart, then subject it to all kinds of abuse. You really don't want your customer to find out the hard way that your lovely piece must be worn in a bubble.