I used DLE 55 mufflers on my G62's, and DLE111 mufflers on my GT80, they work just fine. The muffler mounting flange on the Zenoahs is elongated, or slotted, allowing for SOME adjustment, within reason. The 1mm per side you are all referring to, is within reason
and worked great for me! The DLE mufflers are also among the lightest of their kind!
You can find square nuts at any good hardware store that will fit perfectly into the flange, I believe they were 10/32 if my memory serves me right. I had no trouble swapping out the included muffler blots for the proper length of 10/32 to match up the set and make things work.