As stated before, the upward bend is normal. However, when the frame is flipped over, do the trailing arms for the wheels also stay pointed upward? If so, your axle is probably past it's prime and you may want to think about replacing it. The original specs on the Trillium
axle call for a 0 degree (level) inclination on the trailing arms. If you do replace it, as stated before, you also may want to consider adding brakes!
built their frames pretty stout. The only reinforcing you may need to add is on the bottom of the frame where the front bolts come through. (Unless you really have a hankering to do some welding) There was a recall on the frames as certain ones may crack at that location. Can't tell from you pictures if this has already been done. Search the forums for "Trillium Recall" for more info or post a pic of the front bolt area.
Ahhhh!....More food for thought!