If I do the calculation with for example a Vero 29:
dT = P . dx / (k . A), with
dT = temperature gradient,
P = 50 W of heat dissipation,
dx = 5e-5 m average gap width,
k = thermal conductivity,
A = 7e-4 m2 contact area,
then dT = 3.6 / k, so the difference between k = 1 or k = 10 is just a...