You should be OK since the vertical struts going down to the dropouts take most of the weight of the rack; there is much less stress on the front part of the rack. Several manufacturers make seat post clamps with ears for mounting racks if you would like to explore that alternative. I have taken that approach on one of my bikes and it works well and looks clean. A search on "seatpost clamp rack mount eyelet" or the like will yield numerous useful hits. This is the one I use: http://bontrager.com/model/08427