Not sure if you did this but first thing in 1936 should be to build 2 IC to get to 20 base for a 2nd Tech Team slot. Also I think it would be wise to Immediatly start researching the land doctrines (light infantry) from the start because then you will be up to date when the winter War begins. Also why have troops in unfortified Terjoki at all. Better to let the Soviets assault it and perhaps make counter attacks from Viipuri or just sit tight. As have been said before Kajaani is the weak spot and it´s there that the Soviets will make their first major assault and thus it is there you should put most divisions.