You can get CUZ-LIM for something like $60 with advance purchase on both Avianca and LATAM (LATAM will charge for bags for the cheap fares, though, while Avianca won't, but they have less frequency). Hardly seems worth using miles. We recently did a LIM-SAL-US routing in business using miles and paid for the same day CUZ-LIM segment separately. Upon check-in, the checked us through the whole way with boarding passes and priority bag tags, for what that's worth, even though they were separate tickets.