I think this will be a problem for you when you use the bike, so be ready for it. Professionally made bracketry is usually stiff, either from having out of plane stiffening formed into it during stamping or from being made from thick, stiff material.

Because you are fabricating a one-of bracket (like I also need to do), you can either bend the edges up to create stiffeners or you can secondarily bond stiffeners onto your flat-pattern bracket (use epoxy for adequate strength and weather resistance). After fabricating the bracketry, you can spray paint everything to match the frame.

Can you shoot and post a shot of the mounting brackets taken froom the non-drive side, please? I'd like to see the overall effect. The guard hides the brackets ell from the viewing angles the phtotos were taken from. I'd like to see it from the other directions.

In thinking about my own bracketry design, I was going to attach the front bracket by cutting a large diameter hole and capturing the sheet metal bracket between the bottom bracket's fixed cup and the frame, rather than using a band clamp around the seat tube as you've done. There's lots of ways to do things.

Thanks for the great pics.