It's like this.....,
If your counting on using one side of the Frame as your Border, then you only have the back side to use to attach your cloth too. Than means you cannot use the outside edge of the Frame as a Strain Relief as you pullo, hold, and fasten the Cloth.
Now if you do use the outside edge to pull down over and hold (advisable) then you have to use "Double" Staples, slightly offset at each fastening point. After the material is completely fastened down, fold the extra material underneath and give the Screen a good close examination. If it's "all good" (no wrinkles or creases or bad corners) you then cut the extra cloth so that there is just enough overage on all sides to equal the width of the Trim, then fold it on top of the already stapled Cloth/Trim and tack it down using a minimum of staples / fasteners.
You can't have excess folded across the back with such a "Rear Loaded" design or you'll get "lumps" for sure. But you also need to leave enough material to grab onto if any further adjustments are / ever become necessary. Usi8ng this method gives you just enough, and results in a very clean look at the same time.
Sure is easier to stretch it across the Front, and apply Trim on top the Staples.
But your way does make the assembly look more like a conventional Fixed Screen, with the material at the rear of the deeper trim, and as mentioned, having access to some "grab" might be a game saver.