Just wrap your barrel in the teflon tape, you don't need the electric tape in there. With that extra space you might as well not even do the spacer.
The way I did mine, as it is really hard to pour a little bit down the outer barrel. Because if you try to pour it all down there at once, you are not going to get the inner barrel straight.
Do a little bit, then put the muzzle cap back on.....let it cool, and do it again...and again....and again...and again. Work it up so you can make sure that it is nice and straight.