A Pletscher rack is a silly, flimsy thing and shouldn't be trusted to carry much weight.

I broke a couple of them before I realized I could do much better. If you're a sedate rider and just want a place for your windbreaker or lunch bag to ride, then one would be fine. Otherwise, get a Blackburn style rack, or one of the many that are designed after the classic randonneuring or touring racks which have two or three struts going down to the drop out on each side.