I did this step and the layup on the same day. It turns out that 8 plys of BID are the same thickness as the tongue depressors I use for mixing sticks. Good to know right? My filler blocks just needed to be a good fit with a few sticks thrown in as you see in pic 1 & 2.

The end stick is just to keep any flox away from the rudder cable area that I have spent some time getting clear. I used a heat gun to shrink the envirojoin in the antenna which melted a little bit of the blue foam. I used a heat shield but it still got around that. I’ll be more careful on the other wing..its just a tiny bit but I am being very careful with these major structural layups.

Fitting foam blocks

More block fitting

Foam blocks upper and lower