Double flaring is super easy if you have a nice tool. For stainless steel, you pretty much need a hydraulic flaring tool, but you might be able to get away with a hand crank if your lines are small. I haven't tried in my hand crank flaring tool yet. For the best of the best for hand flaring tools, look to Ridgid.

I have the kit at the end of the list: http://www.coastaltool.com/cgi-bin/S...htm?E+coastest

Never split a line while doing a double flare. The flaring buttons provide a measurement so you get the right amount of overlap every time.

The most important thing when doing double flares, or any flare for that matter, REAM REAM REAM.

If you do go with stainless, I recommend going with compression fittings made by Swagelok.