This may seem like a stupid question but why solder the rack mounting screws?
And why not use panniers, messenger bag, or backpack that you can take with you rather than leave the bag on the rack? Don't any of your coworkers carry a briefcase, backpack, or some kind of bag?
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The Lord is merciful and gracious, slow to anger and abounding in steadfast love. - Psalm 103:8
I am a cyclist. I am not the fastest or the fittest. But I will get to where I'm going with a smile on my face.