I just purchashed myself an RRA Varmint A4 and want to mount a canted scope rail on it for long range shooting, also I was would like one that extends past the standard A4 upper for a little more freedom in scope mounting. I have found the Badger Ordnance piece PN 249-25. But it doesnt look its extended, what other options are out there? Also any personal experiance would be great. Also scope is either going to be a Leupold Mark 4 6.5-20x50mm LR/T or  Mark 4 8.5-25x50mm LR/T M1. I had planned on either Leupold Mark 4 rings, Badger Rings, or A.R.M.S rings.   This is going to be a multi purpose gun. Target, Praire Dogs, Coyotes, and hopefully a little F-Class style shoots

Think LaRue.

    I use an extended riser (1/2" high) made by Accuracy Speaks (available direct or from Brownell's) combined with standard-height rings.  There are now similar ones available from Compass Lake Engineering and White Oak Precision.  This gives me an extra 4" of rail and lets me mount a Leupold 6.5-20x50 LRT (very similar to yours) and gives me the option for an extra 15' of built-in elevation for long range work. I'm using Burris Signature Zee rings - they are inexpensive and work well, even though they don't have the macho look many seem to like.  They use a floating plastic bushing to minimize tress on the scope tube and simplify installation, and offset bushings are available.  Bushings with a 0.010" offset are included with 30 mm rings, and 0.010", 0.020" and 0.030" bushings can be purchased for 1" rings.  They're inexpensive and work very well.  I use them on my spacegun to mount a VX-III 6.5-20x50 LRT and have never had a problem with them.    Also remember that your windage range is restricted when you are at maximum or minimum internal elevation.  You can't apply maximum elevation and windage simultaneously due to the round scope tube.  You won't need large amounts of windage at 100 yards, but you could need 20+ minutes at 1000 on a windy day.  There are minor optical distortions that may be more apparent off center, but the biggest reason to stay on center at long range is to have adequate windage adjustment available.