I found a web site with twinvest /synchrovest type software .
the web site is reversedollarcostaverage.com . it is commercial software about $30.
Interesting find! A way to take money out in a variable format for greatest efficiency as a mirror-image to variably putting it in.
The question is do you need the software, or can you discern the algorithm from their samples and then construct the same thing for free in a spreadsheet? Not that $30 is prohibitively expensive, but if you can do it yourself, do you need the jazzed-up interface?