Cranking the torsion bars, how much of drop can I get?

I just did this to my truck, just wondering how low can I go?How long are these dang bolts? If I keep loosening them will they fall right out? I am supporting the truck on jackstands when I do this, so there is no load on the bars. I just wasnt sure how far I could go before I fawked things up , and maybe couldnt get the bolts back in.

thanks