::sigh:: Apparently rust is bad. Who knew?

[Ldub]

The only thing I can think of is to hold the screw from beneath to keep it from turning and drill out the top. Start with a small bit and make sure it is centered, and increase the bit size until you've drill enough material off the top to pop off the disk.

If Orion's idea doesn't work because of material weakness due to rust...(if the "flower" disintegrates)

I was thinking along the same lines, except where C-J indicates a drill bit or anything related to drilling, substitute mini grinder or dremel...

If you can support the bolt head from underneath, & protect the surrounding paint on top with duct tape/cardboard, then proceed CAREFULLY with a mini grinder or dremel, you should be able to grind off the "flower"...

Same idea, different tool...



Now you have three choices...four if you would give explosives any consideration...

[Cobrajet]

Now you have three choices...four if you would give explosives any consideration...

Hydrochloric acid... that's five!

[Ldub]

Hydrochloric acid... that's five!

I like the way you think...

A well placed, small cal. rifle round would also be effective, but would require removal of the hood...maybe.