I received in the mail today Topeak Explorer rear racks and I scratched my head several times before figuring out a way to install them, however I am not to sure of my work here, the braces I felt could have been an inch or two longer, and they are awful close to the rear break caliper, they do work without touching the braces, tell me what y'all think.
Looks correct to me. You're right about the braces being awfully close to your brake. Is it possible to bend them a bit to improve clearance?
You can probably purchase longer braces. Maybe check on Topeak's website. They might sell just the braces by themselves. I know that "Old Man Mountain" sells different length braces for their racks. Perhaps Topeak does as well.
Close only counts in horseshoes and hand grenades. I wouldn't worry about it. Poor design in this particular regard, but that's neither here nor there.
If it really really worries you, you could certainly take the pliers to those braces and bend them out of the way a little further. Might mess with the angle of the rack, but if piece of mind is at stake.... Keep in mind that the braces are not load-bearing; they simply prevent the rack from rotating backward or forward.