It will be bad. Compare the tempo of SM and Diamond or Jebus-L
Another aspect — the timer must be "resistant to skill variation":
a) It must be such that it doesn't scare off newcomers with excessively high initial timer requirements. Therefore, the 8+4+1 timer for M cannot be universal; let it remain a purely blitz timer. Besides, the player should have time to "space out" at the start of the game, during the scatter, while making the initial plan, and to decide whether to play or not. This "initial spacing-out time" is a constant value and practically does not depend on the map size. Therefore, for M I would propose 12, i.e., 12+6+1.
b) It must be such that the top players can display their top-tier skill and salvage a bad draw — including through time management. Stall the opponent, if you will). This is likely where the upper limit of the Start parameter lies — what it is, I don't know for sure...
