Its hard to remember back to Dans original design with out searching. I just wanted to say that the 3/8" coil spacer seems a little thin to be using with a 5/8" thick stator. I would try to increase it to at least 1/2". This should still give you enough room to fit your windings, and yet have a structurally sound stator casting.
Most stators I have been doing lately are all slightly over 1/2" thick. I mean slightly, like maybe 1/32" over. I use a 1/2" spacer in my winders and I never have a problem.
You will have to experiment with the winding tension. If you go too tight you run the risk of damaging the insulation. Do you glue the interior of your coils? (adding glue as you turn). I have had great success with this method and I always have a very rigid coil come out of the winder. You just have to remember to wax the inside of the winder.
Just my two cents. :-)