YMMV and all the standard disclaimers.

Well... [shuffles feet nervously] I guess I don't always do everything
in the order it's supposed ta be in... [hangs head shamefacedly]...
the fin fairings was supposed to be done long ago...

The balsa supports for the fin fairings went together okay, except
that the die-cut slot in the balsa was too small for the piece that
fits it.  My fault, I should have clamped it, just like TVM showed in
the video.

Widened the slots with a small flat file, just took a few strokes.

The vacuum-form fairings are a fair bit harder to work with than I
thought they would be.  They're *awfully* thin in places, especially
near the bottom where they meet the tube.  Be careful.  They can tear
more easily than some of the other vacuum-form parts.

The edges of the fairings are not straight lines.  I tried laying down
a ruler to cut them before I realized this.  Cut them out with cuticle
scissors as TVM recommends.

[Incidentally, this is one of many places where the video instructions
are clearly superior to any printed instructions.  Cutting out and
fitting of the fairings would have taken a bunch of drawings and a lot
of words, and still wouldn't have been as clear.]

Numbering the fairings and their locations where they fit best as you
fit them may be useful, if you're like me and can't quite cut out any
two of them alike.

TVM uses a technique with Fixit epoxy clay to fasten the fairings to
their supports.  He also mentions the use of Fixit to stiffen the
fairings so they won't deflect.  Stiffening the fairings sounded like
a great idea.  What I did arises from the fact that I use a fair bit
of epoxy in my work.  And also from the fact that no epoxy clay was
handy.  I didn't order it yet.  I'm sorry.  So...

A portion of regular hobby 30 minute epoxy, about 5 mL or a bit more,
was prepared.  A  little bit was rubbed into the balsa where it meets
the fairing, to avoid "starving the joint."  To the rest of the epoxy,
quartz microballoons were added, enough to give the epoxy a good bit
of body (a little more than the volume of epoxy).  The result I wanted
was about as thick as stiff pancake batter or brownie batter.  It
could be stirred, it would flow slowly, but would stay in place very
well when spread thin. [Caution:  the microballoons seemed to make the
epoxy cure more quickly.]

The inside of the fairing was scrubbed gently but thoroughly with
alcohol and allowed to dry completely.  The epoxy mixture was spread
over the inside surface of the fairing (a wide piece of scrap balsa
used as a scraper), keeping clear of the fin slot.  The fairing was
then laid into place.  Alcohol was kept handy and used to wipe off the
excess epoxy around the edges and in other places where it ain't
spozed to be.  It's very important to wipe off the excess epoxy as
much as is practical where the fairing joins the airframe.  That will
be very difficult to sand off later!

After about half an hour or so, the epoxy was fairly stiff but not
fully cured.  Using the end grain of a strip of scrap balsa (doesn't
seem to stick as badly as other "tools") the sides of the fairing were
pressed into place.  The epoxy is stiff enough now, that the plastic
stays where it is pressed.  Alcohol to remove the excess.

The finished product was both rigid and light.  In some trials I had
discovered that the vacuum-form plastic could be peeled away from
cured epoxy -- but not easily.  So I have no fears about the fairing
vacuum-form coming loose.

Dang, I'm runnin outa parts in the box!

P'rfesser