[walker]

Clamp a bar/tube to it that is 5' long or so and bend it down.

 

[walker]

That would weaken it by about half.

No it wont. In fact, so long as it is kept below 1200 degrees it wont affect is properties at all. Might want to do some reading about steel repair. Lots of good videos and written info on this topic, particularly girder repair for the freeway bridges that continually get driven in to by big trucks.