I've used a variable temp heat gun on an Alpha III with bent fins. I started on the lowest setting gradually working the temp up until the fins became plyable. I also noticed that aplying heat to the inward side of the curve would promote the fin twords a straighter postion. I also would over-correct it because upon cooling it would tend back to a curved state, albeit lessened. You just have to keep working it.

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Andrew A
NAR 33674
SAM 0139