First of all aluminum can be VERY unforgiving of cold work. It's already been bent once, and yours will be the second. So the key is to minimize the amount of work and straightening in a single pass. The good news is that the bend is more of a gentle curve than a hard bend, so will most likely be OK to work cold.
Start by finding the angles of bend and twist using the gauge to find the lowest and highest points and bending on that line, so both are resolved together. You'll need to overshoot SLIGHTLY to allow for spring back.
Heat can be your friend, but can damage the paint. I use a deep fryer which allows a controlled temp in the 400F range. If you go that route leave the dropout in the oil for 10 mins or so for a good heat soak. Then be ready to work before it cools.
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FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
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Last edited by FBinNY; 01-22-24 at 04:02 PM.