UPDATE: No elevated radiation measured over different 2cm thick foam block.
It look like bigger cathode is not the best - it likely require higher current. I recommend to use rather smaller cathode that can be loaded faster. Dimension recommended in recipe is fine.
If experiment from Me365 is with H then it could mean that Deuterium is not needed to generate active LENR agent.. But in order to have D-D fusion deuterium is needed of course.