Good suggestions. I agree with your assessment of Winters and his portrayal of Charlie Chan. In "The Chinese Ring," it may be noted that Chan's hair is jet black. With the next film, it can be seen that a touch of grey is evident. I think that the folks at Monogram realized that without this, Winters' Charlie Chan appeared too young. The argument that they were trying, perhaps to "update" Chan and offer a younger detective can be countered by Lt. Mike Ruark's comments, referring to Charlie Chan as "the old guy."
I enjoy ALL Chan films from the series proper, including the Winters entries. I feel that "The Chinese Ring" is a good one, and it shows the strength of the Charlie Chan character to be able to continue to draw an audience after Toler passed away. Winters did an admirable job, in my humble opinion, and, as you state, he had two sets of mighty large shoes to fill!