As far as leaks, I posted this a couple weeks ago as I had a caliper leak: http://www.clubhotrod.com/forums/showthread.php?t=45964

Now, the question as to why 3/8" line? Also, are those lines double flared if regular steel brake tube. If they are SS, you really can't do a double flare without some really expensive tools and even then it should be a specially softened stainless. I purchased my entire 3/16" SS brake line and AN fittings from Inline Tube (http://www.inlinetube.com/) and of course got a few pieces that I didn't use. I also had to purchase the 37* flaring tool for the AN fittings. The Wilwood proprtioning and RPV's are from Speedway.

Using the large diameter stuff, while it will work, just adds a mass of extra fittings stacked up to adapt to the 1/8-3/16 brake cylinders/calipers, other line fittings and the prop and RPV's thus opening yourself to those pesky drips. My problem was easily cured after asking my question - it was a speck of dirt, but to date that was the only drip on the entire system.