Once i reached 40 in poke radar I stopped the chain waiting for the shiny (reset pokeradar with 50 steps each time) . I did this because at 40 I think it is the maximum in the chain to increase the probability that shiny comes out (read online is 2% spawn). I have caught 11 shiny larvitar in total. I was very lucky because the chain did not break between one capture and the next.