Just as a note - GIALLOs were called by that name because they emulated a particularly violent kind of post WWII Italian thriller story found in magazines - the majority of which had a lot of yellow on the covers as a cost-cutting measure. The form existed before the movies did and if the posters have a lot of yellow to them, it was to remind the core Italian audience of the magazines rather than being yellow in and of themselves.
I do, however, REALLY like what I'm finding here and you're doing a wonderful job of emulating the style of the films.