my Crestliner had the same raised/curved bow, so I know what you are experiencing.
I still stand by my prior approval of removing the entire existing metal and making
a new one - either with glassed plywood as you described or a new sheet of aluminum,
braced appropriately from underneath.............
when you end up with the flat bow surface, your TM should install as it was designed to.
in my very personal opinion, using shims and spacers to make something fit outside
of its intended design, looks just plain shoddy and may not perform as required.
my recommendation would be to use new aluminum so it will fit under your nose cap.
from what I see, plywood will not fit under or flush with the nose cap. (take that into consideration).
jus my Dos Centavos
and for Heaven's Sake, please trim those zip tie ends !!!!
.