[Jeff-Groves]

It may seem hard at first if your not a hex editing Guy!
But it is really simple once you do it a few times.

1st
I export the deck to an object file. What you use to do that does not matter.
No tool out there will give you the EXACT vert information! They all round to 6 places and that is where the secret lies!

Next,
I edit the exported object file in any 3D program to have just the area I want.
I delete anything not important to the area we want to edit.
Then save the file as 2 different obj files so I can compare them.
I end up with 2 faces in each obj file and 6 verts in each.
I'm only interested in 4 verts in each file. 4 of those are the ones to adjust!

At this point you should have 2 files that look like this in note pad.

Forward section...........

# 3ds Max Wavefront OBJ Exporter v0.97b - (c)2007 guruware
# File Created: 26.02.2021 10:04:53

#
# object NSS_Uboat7b_deck_41
#

v 0.102030 0.141436 -2.210532
v 0.104960 0.144917 -2.081790
v -0.102031 0.141436 -2.210532
v -0.104961 0.144917 -2.081790
v 0.000000 0.141436 -2.210532
v 0.000000 0.141436 -2.210532
# 6 vertices

g NSS_Uboat7b_deck_41
f 6 3 4
f 2 1 5
# 2 faces

Rearward section.........
(This one I exported with 12 precision but that didn't help)


# 3ds Max Wavefront OBJ Exporter v0.97b - (c)2007 guruware
# File Created: 26.02.2021 09:17:14

#
# object NSS_Uboat7b_deck_41
#

v 0.098945997655 0.138082996011 -2.316945075989
v -0.098947003484 0.138082996011 -2.316945075989
v 0.101992003620 0.141395002604 -2.211843013763
v -0.101993001997 0.141395002604 -2.211843013763
v 0.000000 0.141395002604 -2.211843
v 0.000000000000 0.141395002604 -2.211843013763
# 6 vertices

g NSS_Uboat7b_deck_41
f 6 3 1
f 2 4 5
# 2 faces


You can copy the above info and save as an obj and get both my working files.