Ruger should probably have looked at their own past history as to how popular a .22 Mag. only Single-Six was.
The Mag. was first introduced in 1959 as 6-1/2" barreled model. Not long after, folks began sending their .22 LR only Single-Sixes in to have the Mag. cylinder fitted to it. By 1961, Ruger figured out what a great idea this was, so came out with their Convertible model Single-Six in all four barrel lengths.
By November 1962, very few Mag. Single-Sixes were coming out of the factory and after that date I know of only eleven guns over a serial number range of 342128 to 389108 that were factory shipped as "Mag. only". After this, no guns were shipped as Mag. only except for a small run of maybe only 15 Super Single-Sixes with 6-1/2" barrel in the 555xxx range.
Long story short, the market conditions made the Mag. only Single-Six obsolete. People like the "value-added" idea of a Single-Six with two cylinders even though the Mag. was rarely shot (if shot at all) by the majority of owners.
The gun to put away will be the Single-Nine .22 Mag. only. Look for Ruger to turn this into a convertible before too long. This should not be a huge deal in the way of manufacturing as Ruger would literally make the 9-shot L.R. cylinders first, then simply ream out for the .22 Mag.
How about .22 LR only Single-Sixes through history? Well, again...after the convertibles came out in 1961, Ruger made maybe only 5% of their O.M. fixed sight Single-Sixes as LR, a small demand from the public that warranted a separate (cheaper) model who knew they would never use the .22 Mag anyway...(DUHHHH!).
After that Ruger tried the star model LR only NM Single-Sixes in 1975...which was deemed a failure after no more than a year.
Not content with letting dead horses lie, they tried again in 1986 with the "arrow" model LR Single-Sixes (discontinuing the convertible models while the "arrow" models were in production). FAILED after only a few months of production.
I really think Ruger will be making a Single-9 Convertible very shortly, which may even make the 6-shot Single-Sixes obsolete.
Chet15.