if that is your brake its not bad....looks like there is no adjustment for it though. does it have "fingers" that you can remove?
just looking at it i dont think you have too much to adjust or fiddle with. the two T shaped things at each end, if you play with those doed it move the clamp part up and down? if so there is how to get so it it dosent slip. if you cant get it tight enough you might just have to employ a shim or something like 450 dude reccommends. if there is something on the back side you could clamp to the try getting some vicegrips to hold the work while you bend.maybe you could vicegrip the front if'n it didn't get in the way of your bending action.
a lot of brakes when they get a bit longer, like more than 30" or so will clamp better at the ends than the middle. most manufacturers throw in a "truss" if you will, a thick metal arch with some adjustment nuts. this helps keep pressure even on the work as your bending longer stuff. most times there is a matching "truss" on the bottom as well so you dont just bend a big smiley face. you could try something like that. along the same lines...put the stock to one side or the other, dont try bending in the middle of the brake.
remember....just 'cuz it sais it can do it dosent mean its gonna do it willingly. i have a 4' brake rated @ 16 guage. I almost have to have somebody help me bend a 4' sheet of 18 guage. I hate to say it but if its a HF model, it just might no be manly enough to make the bends you want in the 18 guage. it kinda sounds like you have two options....
1, modify it so you can adjust it a bit more
2, live with the unit as-is and work around how to clamp the work in.
P.S. i've found it does nothing to improve the situation but sometimes cursing at or hitting things that dont co-operate makes me feel better.
