I typically make a custom rack for my bikes. Centerpull brakes require a 4 point connection, using the brake pivot bolts as 2, and some bits brazed on further down. Of course, this ruins the paint, so it's only done on frames that will get a lot of other mods, typically. My Centurion Pro Tour "Zero bike" original finish is too nice, so a Mark's rack was used, along with a custom decaleur. I can make the extension length so that the bag doesn't interfere with hand position. The "standard" Velo Orange decaleur extends 10cm from head tube centerline. I've made the extensions as long as 15 cm, with little ill effect on handling.
pic courtesy of @djkashuba, 2019 TdMIL