I'd suggest a soft structured carrier (brands like the patapum, ergo and the lovely yamo)
or a non-stretchy wrap for your 9 month old. Either will be great for front or back carries, and with a long baby back carries will be more comfortable.
For a bigger newborn, a slightly stretchy wrap like the moby is preferable to the very stretchy hugabub. The moby is wider and able to be used for much bigger babes and is suitable for back carries. As a bonus, it's about half the price of the hab
What kind of carriers did you try? Structured ones like the baby bjorn, ring slings??