I would argue that 1.5mm ally is the maximum?

I've only got a medium sized bench vise - when bending steel, I tend to use two chunks of hardwood, sandwiched round the steel, clamp eveything in the vise and then use a bit of brute force, and then fettling with a plastic mallet. If it's more than 3mm steel, I'll use a bit of heat.

"Y mae dafad ddu ym mhob praidd"
1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10