I've a set of time trial bars which have internal routing for the cables, but no holes at the end near the brake levers (the horns of the bull as it were). The nice aero looking brake levers all seem to have external routing, what do people think about drilling just after the brake clamp to feel the wire insided (there is already a hole by the stem), I figure there can't be much force on the bars there without any leverage? Otherwise any suggestions of bar end levers with internal routing with nice aero lever shapes?
'''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
As long as the manufacturer provided the drilled holes by the stem you should have no safety issues with drilling holes near the bar ends provided you do a smooth job and don't leave any stress raisers. Your right that the leverage at that point is quite low.
However, the externally routed cable housing will have to make a pretty tight turn to feed into the outer hole so that may have a negative effect on brake operation.
When I've bulit bikes with those bars I normally use the levers that have the cable come out of the back of the lever plug instead of below. If you use the latter setup it might be easier to just route the cable externally to avoid the sharp turns.