An interesting calculation to make would be the strength in bending and shear of the CF steerer and the dowel of slightly smaller diameter. I'd also do the same with a traditional steel steerer as a reality check. If the work is up to the levels of either the steel or CF, I'd have no worries - if I knew I did a good job. I would not include the epoxy in the calcs but I would use plenty and with real care to get everything bonded and the crak between the steerers filled.
Ben