Joe Meek mounts are not the correct size for the SE300b bodies. I know because I bought those mounts and they were too large for the mic bodies. What I ended up buying are the Studio Project C4 mounts, which do fit the 19mm bodies (that the SE300's are) just perfect. You can find them here
http://pmiaudio.com/accessories.html (look for the "Replacement shockmounts for C4" about 1/2 way down)
Now if you want to mount them as actives, the kwon bar won't work as I've tried that too. I ended making my own DIY bar out of some 1/2" cpvc tubing and (2) 45 degree angle pieces (also cpvc). If you want a picture, I can take one, or you can search out pictures of DIY projects somewhere in one of these threads, plenty of photo's out there of DIY projects to be found if you search them out.