My local LBS and I talked at length yesterday about your sizing issue nothing seems to indicate that you need a custom frame. It will get confusing wether you are using a sloping top tube or staight top tube or for that matter 700c tires or 26 inch, mountain or road frame, or staight or road bars - but lots can be done with size of stem , spacers, and crank arm length. Because everyone is making a plug for a custom frame builders - R&E cycles in Seattle - they make a lot of touring bikes for women for pretty reasonable prices if you are thinking new.