I have a number of old (10+ yrs) white &slightly raised hypertrophic scars on my arms.I am currently using an at home Derma-roller every few weeks,which does seem to be improving the texture,however I wonder if Laser could provide a more significant improvement?If so,should I go for CO2 or Erbium? Also,I have two long flat surgical scars,from Scar Revision,which I would also like to improve.The skin is much thinner in these scars so I have not used a Derma-roller here,what's the best treatment?