Oleg, some times ago I replicated the circuit described in their patent, using the same vacuum tube: zero increase in capacitance. They later explained that the actual tube required for obtaining the effect is very different from the one cited in the patent, but at this point I'm very skeptical. BTW, if I remember correctly, J.P. Biberian has done some investigation on that and he reported some preliminary (non-negative) results. But I heve no detailed information or updates.
Care to share what tube exactly is needed? Patenting different tube seems sketchy.