When I flew a/c with both speed tape & ASI I always looked at ASI. No-one explained how to use the speed tape. Then I flew a speed tape only a/c and the chief trainer took the time to explain thoroughly the speed tape and all the data there-in. What a relevation, and I never looked at an ASI again. I now fly speed tape only and do not miss an ASI at all. The secret was a good proper trainer taking the time to do his job and help his colleagues. Vital.