I don't know if drop a carb add a fat is at every meal--I think maybe just one meal a day? Maybe not, I haven't got a really straight answer yet. (help here?)
But... (now for my 2 cents)
I have found that certain combinations hold me longer than others. This can do with a combination of low and medium glycemic carbs (broccoli + whole rye bread is better than apple + whole rye), different types of proteins (for some reason, cottage cheese sticks with me, turkey--not so much!), liquidy carbs (applesauce and smoothies don't hold as long as oatmeal--and I have to use the bathroom more often!), and even activity level (I am more active in the late afternoon, and need to add fat to my snack or I am in trouble).
Have you tried experimenting with anything other than the ingredients you listed? Personally, I'd get very bored with the same thing 21 meals a week! You must be snapping beans until the cows come home. :)
Also, instead of salt, you could try adding lemon juice, pepper, cayenne, garlic powder, creole seasoning (my favorite, has salt but you really don't need but a sprinkle) and various herbs to your repertoire. I find easy ones for veggies are dill weed with lemon, and either the Creole seasoning, Old Bay seasoning, or Italian Seasoning. I like to experiment with lots of herbs and spices, but keep these handy for a quick sprinkle.
Good luck with your experiments!