Hey Craig, you are hitting on a minor variation that hasn't been catalogued as thoroughly as more significant changes. None-the-less it could be interesting to a Sioux City / Iowa collector. Using Weber as an example, all five poses are known with "s", only three are catalogued without the "s" but suspect you are correct that all poses can be found both ways. Let me know if you find poses 3 & 4 without the "s".
482-1 Bat at ready, looking at camera
a. Weber, P., Sioux City (Fc)
b. Weber, P., Sioux Citys (Fc)
482-2 Strike, looking down at ball
a. Weber, P., Sioux City (Fc)
b. Weber, P., Sioux Citys (Fc)
482-3 Pitch, hands at chest
a. Weber, P., Sioux Citys (Fc)
482-4 Pitch, hands out waist high
a. Weber, P., Sioux Citys (Fc)
482-5 Pitch, R/hand chin high
a. Weber, P., Sioux City (Fc)
b. Weber, P., Sioux Citys (Fc)