On the presumption that it is more fulfilling to catch a fish you have specifically targetted than to catch whatever comes along (although that isn't of itself an unpleasant way of fishing), I would agree with Gary - I don't like the idea of a "scaled down barbel" approach to catching chub.

Two reasons: first I think that you can't actually "target" chub in the way Robert suggests; and second with this approach you will be highly likely to catch barbel and risk break-offs on lighter tackle. Fishing more traditional methods for chub will occasionally result in a barbel but not with the statistical likelihood of pellet hookbaits.