Keep leaning towards the Bald Eagle. IMHO its the best going... Anyhow, what I do with mine (& I have the windage top on mine) is I just use the applicable size bag on the rest plate. For my sporter stocked rifles, I use the narrow 1.5 - 2.0" bag. I have a 2.5 - 3.0" bag for the wide stocked rifles (which I don't currently have). I have not looked in Bald Eagles line, but I do know sinclairs & hart make an adjustable top to do what you desire. I have used that style and did not like it, I found it far easier to change the bag than to adjust the top plate to the stock..
With the bald Eagle, you get one bag w/purchase and for another 20 or so $ you can buy another bag for the other size stocks..
I bought my rest from Bill Krazinski at Allied Shooters Accessories and here is the web address. http://benchrest.com/asa/
Awesome customer service and great price, give him a look...