Hi Michael,
So I fooled around with his area, and come to that "n-sided patch" command... (I think)

Here is the model as a solid, with a pre-fillet model in it and a couple different results from it... Mostly, the fillet makes a sharp transition in the rear of the fillet. (Style Blue-Object "problem area") I've left a couple different types of open areas in the different models.

Looking at filling these in, Whether starting from the front or back as the crux, could you elaborate on the tool for me.. I looked at patch in Rhino and didnt make sense of what i needed to do.

Also, perhaps a variable fillet will perform here? as a smaller fillet will work, but to get the large front part, that transition goes out.. Using blend, I always end up with the last patch that needs filled while maintaining more than 2 tangencies...

Thanks for the time.