A few years ago I replaced 2sj79 and 2sk216 with ksa1220 respective ksc2690 on both Blue Hawaii and T2 and that without changing any voltages.
Below chart show voltage cross source and drain on T2´s Q26,Q27 during power on, 30 second wait and power off.
So far I haven’t had any ksa1220 or ksc2690 blowing up.
Today I reduced voltage further on my T2 PSU, 300V section now 200V. Seems to work as good as with 300V. High voltages are now +/-400V, +220V, -260V and -460V. The reduce voltage also lowered the maximum voltage on graph above to 200V