Need help limiting the "cone" or field of view on mmWave sensors c4002(SEN0691) and SEN0395

Hello -

I have been experimenting and having fun with the mmWave sensors c4002 and the older SEN0395.  Currently I'm trying to come up with a way of narrowing the field of view - especially on the c4002 since the FOV is ~120 degrees in both vertical and horizontal. 

120 degrees is quite wide for the project I'm working on.  I've tried a few different methods and materials but the only thing that has worked so far is a steel “soup” can with the top removed and the bottom left intact.  I place this over the sensor face and this seems to completely block the mmWave signal, which is a good start.

I have also previously tried aluminum, glass, tile, zinc paint and various plastics but the signal seems to easily penetrate through all of these.

I am tempted to try ‘conductive shielding paint’ which is used in electric guitars and also have found ‘faraday tape' which sounded interesting.

Does anyone out there have any experience with these materials or methods used to either absorb/block or otherwise limit the field of view on this type of sensor?

It seems as though using 5m mode (20cm resolution) might also reduce the FOV cone?

Any advice would be much appreciated! Thanks for reading!