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antimonysarah, can you post a photo of what you're working with? Worth a thousand words and all....
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gugie makes custom racks, and there are others.
There have been several bag supports that mount to the stays, but I'm not aware of any current models to recommend. There's an English one called Midlands that is to be avoided. The one made by Park Tools (I thinkt) i the 70s was good, but hard to find now.