Well I finally got around to modding a single Smart White Titanium 0.1dB.
Cutting with a hacksaw and cleaning the surface with a broad file was relatively easy.
The problem is the remaining flange diameter is three millimetres too small to fully encompass the four C120 flange screw holes.

Anyway I did some comparative testing on 5E, BBC World.
In all cases I did not move the dish, I only adjusted the skew and more importantly the focal length to optimise the signal strength for each LNB.

My dish is a very old 180cm prime focus with F/D of 0.468 and unknown feed horn.

With the LNB I'm currently using (Inverto White tech 0.3dB) I got 73%.

With modded Smart White Titanium the best I could get was 69%.

Finally I tried my old black Invacom and got 76%.

Therefore, I've left that in place!

So, to conclude. The modified Smart White works fine but not quite as good as the dedicated C120 LNBs with my dish and feedhorn.

Interesting afternoon in the sun