Welcome to quantifying shit you already knew

Look at this graph.
It's the Guts formula.
In the late-race, the Y axis is the hp drain multiplier, and the X axis is your guts stat.
300 guts is 1.47x drain
400 guts is 1.4x drain
600 is 1.33x drain
1200 is 1.23x drain

none of this fucking matters tho because much like bakushin campaigns ignore stamina alltogether, the invisible 400 guts + your base stat already puts you in the red circle, around 1.37x drain for 1/3 of the race, and going from baseline guts to 1200 would only save you 4% hp across the whole race.

So don't fucking touch the guts button unless its year 1 and there's strong incentives piled up on it coercing you to do so.