Man I remember trying to get the plate to turn. I finally used a pencil torch to soften up the loctite. It took awhile because of the small flame. I wouldn't have wanted to use anything larger like a propane torch.

 

I used the PB Blaster on mine, and it did the trick. Had to use a cheater on a homemade spanner to get it loose, but once loose it is fairly easy to adjust. As someone else said, do not leave them at one end or the other without backing them off an 1/8 of a turn or so. It might take a day or two of soaking with the Blaster, but it will come loose. I did mine with the bike on the jiffy stand. A little cramped, but got the job done. Be sure to spray the Blaster through the spanner holes, and on the bolt on the outside.