All the ways to assemble an inner cover made from masonite are wrong.
Masonite is garbage and won't stand up to the enviornment of a beehive for
very long before sagging and peeling off attached to wax and propolis on the
frames.
   If the bees are putting nice white wax on the inner cover you are late in
getting your supers on and are missing part of a flow.
   I scrounge 1/4" plywood for my covers and so far the best is the Baltic
birch that pressure washers from Sweden come in.  Ask around loading docks if
you are looking for scrap to make your own covers.. Lots of metal things that
have been painted use 1/4 ply for shipping along with cardboard.  Garden
tractors , pickup truck accessories etc.
   A flush trim router bit like is used for laminates makes short work of
cutting covers, you just tack them to a super and go around it with the bit
and you end up with a piece the same footprint as a super.  Nail and glue a
rim on it and clinch the nails back so they cant pull out and you are off and
running.
   I use old queen cages for a spacer between inner cover and telescope. They
also come in handy as a prop to hold supers apart while you pry the frames
down.
   All ina ll a good flow but a late start in the Northeast USA but a drought
if this weekends rain doesn't materialize.

Happy Beekeeping.