Hello Zink,
If you want to drive at Wr. Neudorf indoor, I can give you my last years configuration.
Motor: Nosram 4T octa wind
Boost 3-4 at LRP - but this year it is a hobbywing 1S ESC
gearing: 96T/25T
rear tire: 44-45mm outer diameter
front tire: 41-43mm
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so with your 6.5T I suggest to gear it up or boost it more
but it always depends on the track layout
if you have a lot of tight corners (more 180°) use lower gearing for acceleration and for the straight give it more boost..........
look at motor temp after every 3-4 minutes
greetings from vienna
Harald