It really does sound like we both are in a similar situation. Ashley sounds like my Sadie, and Gaylord sounds like Hiro. Hiro is also a thin cat. He is at a perfect weight right now and if he were to lose any, he'd be skin and bones too.
Both Aki and Hiro are my roommate's cats, so when we eventually go out seperate ways, I'll just have Trixie and Sadie. When that happens, it'll be really easy to control Sadie's weight, since Trixie is already getting seperate meals. That could be a a year or 2 down the road though, and I don't want to put off dealing with Sadie's weight problem until then if I can help it.
If I figure out a way to get her to lose weight, I'll be sure to let you know