Awesome post, I really liked how you talked about some of the pitfalls like sewing the loose strap end to your piece and the seam/hem description was perfect.So you want to make your own dropbag huh? Here is how I made mine.
I personally hate using pins and for the drop bags I have made, I draw a line with a long metal ruler on the mesh (and x's where the webbing should go so you don't get confused about which side of the line) and square up the webbing with the line as I sew it on, ditto for the top webbing, I throw a couple of clips on the edges/ends just to set my length.
Best clips I have found are Clover brand, cheaper ones just don't have the bite:
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I find it easier to sew the edge hems before sewing the corners, it does take some thought about which way the hems will end up.You'll notice three things if you look close. First I pined the strap tails so I wouldn't inadvertently sew them to something, second the corner has one side taller than the other. This is because we haven't hemmed it yet. Lastly, the bag is inside-out.
Next hem the un-hemmed edges so that they are the same height as the other piece. Be sure and fold the fabric the right way.