YMMV and all the standard disclaimers.

Paper part of the big transition:
The CA glue coating didn't stiffen up the paper part of the transition
as much as I'd have liked.  I now wish I'd made another couple of
transitions to go inside the one supplied.  I would have made them of
cardstock and about five millimeters shorter so they wouldn't foul up
the fit at either end.  Don't glue them in until the fit of the
transition provided has been properly adjusted.


The big transition wrap:
Problem:  The wrap for the transition is too short.  Some of the other
wraps have been a bit short, but I've been able to stretch them
slightly to fit.  On the big transition wrap, the ends meet but
there's a smooth place about two corrugations wide.

Attempted solution:  trim about a millimeter off the inside curve of
the wrap.  That cuts off the very ends of the corrugations.  Now the
wrap can stretch a little more.  Unfortunately, there is no way it's
going to stretch an eighth-inch.  This trim that I did was probably a
bad idea.  I had to seal the ends of those corrugations before
painting, so the paint won't seep underneath.

Possible solution:  glue it in place and make a couple of plastic or
balsa corrugations to fit in the space.

Actual solution:  glue it in place, turn rocket so I can't see the
blank space.  :)

The conical shape makes it a little difficult to fit the wrap
properly, tape it into place, and have it stay there.  I need three
hands and a prehensile tail, methinks.  So:  I got the fit correct,
then slid the wrap forward a bit and taped the ends together.  Then
slid it back, pressing it snugly (not too hard) onto the paper
transition.  Nice, tight fit and I can hold it with one hand, apply
glue with the other, wipe it off with the third.  No need for
prehensile tail anymore...


Electronics:
Something I hadn't considered is electronic recovery.   
Shoulda-but-didn't:  cut a 38mm hole in the forward centering ring, at
the edge.  Mount a piece of 38mm airframe tubing maybe 6" long aft of
the centering ring, cap the aft end.

Since I didn't do any of that, I'll probably have to mount any
electronics in the forward end of the 29mm motor tube.  Or possibly
glue a 29mm tube to the inside wall of the main tube and mount a MAD
or an accelerometer there.

P'rfesser