Help! Weird issue with Zastava m77 Adapter plate

Hey guys,
I defer to the collective wisdom of the community on this one. So I ordered an adapter from Desert Fox Outfitters for my slant cut Zastava m77 part pk1025 (http://http://www.desertfoxoutfitters.com/commerce/product_info.php?products_id=693) to switch out the ugly thumbhole stock for a skeletonized Ace LTD stock I bought online as well. Anyway it just showed up today, and to my dismay it doesn't line up perfectly. The inward "angle" of the adapter starts to slop in too late. When mounted it creates a gap in the sides and actually ends up angling the adapter plate a degree on two downward. Is there a possibility that the part was machines out of spec ? I have tried to shim the adapter by placing a cut piece of a cord reinforced heavy duty rubber washer in order for it to line up properly. I have attached some photos. One with the shim and one without. When I tighten it down with the half of a rubber washer in there the mount is solid no flex to it even when I attach the stock and push down on it with all my might. Its "viced" pretty well in there. It doesn't budge of course either without the washer either, but looks a little bizarre. Obviously there is a little bit of a gap on the side there, but that doesn't really bother me. I contacted Desert Fox so I'll see what they say.

What do you guys think? Should I just run it with the rubber washer wedged in-between, or accept it without it. I update you guys when I hear back from Desert Fox, they are great guys and shipped my item out really fast.

First photo is without the washer, 2nd photo is with it, 3rd is of the washer itself.

Thanks guys

More photos!

Just got some responses from Desert Fox from Allen. He was very helpful, and stated I could return the adapter plate if I wanted. He said this issue is one that he ran into only twice before and was trying to figure out if there was sort of pattern, and had even gone so far as to call overseas to Zastava in Serbia. He did say that the other 2 occurrences of this problem the 2 individuals found the actual ace Zastava adapter (AKRBZ http://riflestocks.com/store/product120.html) didn't have the same problem. So it may look like I may need to buy that adapter then . Has anyone ever shimmed a stock before with a rubber washer or other such system before? I just wanted to make sure my basement gunsmithing, would hold up. Allen from Desert Fox came up with the idea of using a piece of tig weld aluminum as a spacer. My rubber "crush washer" shim seems pretty solid to me but wanted to see if there were other ideas (or if you think what I did is good enough) as I am pretty green to DIY gunsmithing type stuff and make sure I'm not overlooking something. I have heard that ACE has a unusually long wait time for shipping items out.

Feel like this is turning more into a gunsmithing thread but oh well . Has anyone else ever shimmed a gun stock before? Any advice or help is welcomed. Thanks guys

For those of you more visually oriented, like myself here are a few more photos