Dan, unfortunately I can't help with the 44-40 loading, when I went shopping for my first cas rifle, I wanted 44-40 but couldn't find one, so I settled for 45. While I do enjoy the 45, I've always yerned for the 44-40, just because??? I don't think there's gonna be that much difference in the two. I really believe the SPG grease cookie is going to be unnecessary to the point of diminishing returns, one more variable in the load to lead to inconsistancies. They said that the 45's wouldn't hold 40 grains either, they were mistaken, I know of folks that have gone as far as 43-45 grains just to see if it would hold that much and still seat the bullet. It will. I do however recoment the fiber wad, I have never used wonder wads, but I do use a beer carton wad. I don't know why but it does run cleaner. My 45 loads are 37.5 grain average, cause that's what my homemade dipper throws and it works well. The only problem I've ever heard of in loading the 44-40 was that the bottle neck was pretty thin and if you're not careful when sizing and bullet seating, you can easily crunch the neck. I think a case full of 777 would be a hoot to shoot, infact I had decided to pick up a pound this weekend for that very purpose.
I'm sorry for having rambled, but I'm too lazy to edit. I'd really like to hear how things go, so If you would, keep us posted