Ed,
I have an Accushot 1 piece mount on my RWS 350 Magnum that I shimmed in order to compensate for barrel droop and it worked great. I shimmed the rear of the mount with 35 mm film strips, I think I used 3. Prior to shimming I was all clicked out on the vertical adjustment and was still shooting at the bottom of the taget. After shimming I got the POI dead center and the click adjustment now had plenty of "room" for future adjustments.
I have to admit I was very nervous, this being my first attempt at shimming, but I made sure I was extremely careful when it came to tightening down the now shimmed mount, and it worked out great. I know that some people will tell you to go ahead and shim and some will advise you not to do it. I also have read that if you're not careful when shimming you can severely damage your scope. I certainly am not qualified to advise you whether do shim or not, I can only tell you that in my case I was willing to take the risk and it worked for me. Whether you should do it is of course a personal choice on your part based on your research.
There is a shimming guide posted in the GTA "Library" section, I used it to determine how much to shim. Anyway,,,,, good luck with whatever way you choose to go.
Jeff