From the description it sounds to me like its flat transverse and raised but bowed much as a swamped rib would be. The distraction could be worse. You should look down the rib of my Smith 16 ga FW. Waves and steps, oh my! Irregularity of the planar always raises the spectre or hafasst redo but it also doesn't make the Gods jealous and the birds probably won't care either.

jack