Pilot TV-37 question

[bigaudioal]

Starting to tear into my Pilot TV-37U (with ballast tube). Noticed that the SAMS (62-16) matches the set rather than the Rider. The 3KP4 CRT (V21) does not appear to be first in the filament string and my set has a ballast tube listed as M4.

I have heard that the CRT filament needs to be protected b/c during startup it overheats b/c of too much voltage draw until the other tubes in the string heat up. Is this the case in my set where there is a ballast and the pic tube filament does not appear to come first in the string? Should I still take the measures to protect it? I was thinking of installing a CL-90 thermistor at the place indicated by my pointer in the below photo. On the AC line before the 33 ohm 4 watt resistor. Any advice would be appreciated.

Thx.