Skeleton coil forms, Big coil update

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jason Johnson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <hvjjohnson13-at-hotmail-dot-com>

I was thinking about the construction of my BIG coil (June 2nd, Few questions
about large coils), and about a comment about my planned secondary of 12"x54"
close wound w/ 21 guage magnet wire, was way to small for 17 KVA, and it hit
me- you can make a secondary twice as big with the same amount of wire if you
double the wire spacing (this should have been obvious earlier but oh well). So
I'm now thinking about building a 14" x 100" secondary on a skeleton form with
with 21 guage magnet wire and with the spacing equal to the wire diameter. Now
this is easy enough, I just wind two wires on and take one off after I'm done
(I have three 14lb spools of 21 guage magnet wire but I need two for other
projects). But the problem is now how do I coat it? half of the surface of the
secodnary is going to be open with nothing underneath it. Do I need to coat it?
I know from personal experience that magnet wire under tension with nothing to
hold it (like polyureathane) does stretch over time and may become loose on the
form, but I have no Idea how much 21 guage wire stretches (or even if it will
at all, all my other stuff is finer than this). How many other people have
built large secondaries on skeleton forms?