As pointed out by Devine in his article, you can get a unique identification number for any collateral relative in any line of descent by using the Sosa-Stradonitz number of the common ancestor, followed by a decimal point and an expansible descent number based on the Modified Henry System (the first child of your ancestor No. 128 would be 128.1 and so on; Devine points out that if 128.1 is also your ancestor he would additionally have the number 64 in your chart). Spouses of those in resulting descent files can be given unique numbers by adding the letters a, b and c for spouses 1, 2 and 3 of any given individual. William Dollarhide, creator of the Everyone's Family Tree, goes even one step further in recordkeeping with his software. Bill puts an asterisk before the letter identifying the marriage number (so spouses will sort separately). He also can create a "new" ahnentafel for each collateral ancestor by adding a colon to the end of the ID No. and then adds the "new" ahnentafel number. If, for instance, the brother of your grandfather is 16.1, his first wife's number would be 16.1*a. If you desired to include her ancestors in your database, then her "new" ahnentafel number would be 16.1*a:1 and her father's number would be 16.1*a:2, etc.
Always keep in mind, however, that ancestor and descendent databases are two distinct things. A DIGEST reader pointed out: "The primary problem with numbering systems is the frequent effort to mix ancestral numbering with descent numbering. Like oil and water, they do not mix. They start at opposite ends of the scale." He noted that if you are keeping a record of your own ancestors, you should use the Stradonitz system; if you are writing a history of the descendants of one of your ancestors, you will need a different numbering system.
For instance, I keep records on all Pences I learn about. I use the Modified Henry numbering system for those 11,000 records. But only about a dozen of those are ancestors of mine, so I have extracted these and include them in an ahnentafel-based system along with my other ancestors.