Connectivity Mark Net for temporary layers

I'm creating a temporary layer on the fly if a user wants to combine
layer stackups for EM simulation. As an example M7 anded with M8 that
enclose V7 will create a temporary LSW layer M7_M8.
I've been trying different technology file skill commands to create
the correct connectivity between the new layer and the old:
M7 or M8 butting M7_M8 is a connection.
Using techSetEquivLayer it works a little:
techSetEquivLayer(techId list("M8" "M7_M8"))
techSetEquivLayer(techId list("M7" "M7_M8"))
Connectivity->Mark->Net, click on a M7_M8 fig, and it marks correctly.
Connectivity->Mark->Net, click on a M8 fig, marks stop at the M7_M8
fig.
If I create two M7_M8 figs that overlap, Connectivity->Mark->Net,
click on a M7_M8 fig, mark stops at the clicked fig.
Any answers or guesses are appreciated.
Thanks,
Mark