You might be out of luck unless you have a rather large straight section in the centre. On a related note, just throwing aero-bars on a bike will usually result in a bad fit; after a 15 mile commute with new aero-bars my shoulders felt like they were going to pop out of their sockets. The position was too stretched out for use with aero bars, even if it was perfect with drop bars. Having two wildly different hand positions will necessitate a compromise in fit; what works for one will probably not work for another.

Instead, I would suggest using a new stem that would put a flat handlebar at the same level as your risers are currently. Or, once you have the height settled using a new stem, you could try a wider assortment of handlebars. I'm a fan of lots of sweep, and there are people out there who swear by trekking bars.