Here is a photo of "Reesie Jouet" showing precisely the section that will be rebuilt on "Lil' Mule II" as seen from the front. Not that the mast has been removed for a clearer photo:
Jouët Caprice roof

Below, you can see the same area, from the side. This gives me the angle and the corner dimensions for where the two halves of the roof meet. This also shows the distinctive shape of the window, which on "Lil' Mule II" can only be seen from the inside at present.
Jouët Caprice roof

The lines correspond to the following measurements that Joury made from "Reesie Jouet":

a = 33.9 cm
b = 37.6 cm
c = 5.4 cm
d = 7.8 cm
e = 15.6 cm
f = 5.4 cm
g = 16.4 cm
h = 63.5 cm
i = 8 cm
j = 10.8 cm
k = 12.9 cm
l = 4 cm
m = 2.8 cm
n = 133 cm
o = 37 cm
p = 11cm
q = 28.1 cm
r = 103 cm

One thing which I find surprising is how they are not round measurements. I tried converting them to inches to see if they were round in inches, however, there too, they are not whole numbers, except for h, which is 25 inches. This must be because none of the surfaces are square, but rather, rounded or built on angles. This of course, does not matter at all, but I did find somewhat surprising.

Here are some additional detail photos from "Reesie Jouet", which will help create the plug: