Also, keep in mind that...
...a 1-20 spread is not necessarily optimum - if you are in a "play-all" counts mode a 1-50 spread (ie, 2 hands of 25u) is best... BUT a 1-10 spread (ie, 2 hands of 5u) is quite sufficient if you are able to ONLY PLAY POSITIVE COUNTS.
And, in any event the level3 UstonSS is not the ideal count when several balanced and unbalance level2 counts will equal USS in million-hand simulations, and most level1 counts, like HiLo, are entirely adequate. zg