one more demo of the diff in boost drive vs B+ to the horz osc and effect on HV. because of the way the set is wired the G2 on the CRT gets what ever the plate load resistor for the horz osc gets as well so the brightness increases is prob more do to the G2 than the HV but I am sure the extra HV does help brightness as well.
http://www.youtube.com/watch?v=dEiGWFisXMA