Is is possible to use multiple panel types on the same inverter?

From Eric Every at Solaectria:

"When installing an array with different make and model modules it is important to find modules with voltage, current and temperature characteristics as close as possible. The best way to do this is to find modules with the same cell type and cell count rated for similar power levels. It looks as if you have been able to do this with the Trina 230 and the Hanwha 235. Cell type, cell count, voltage and temperature coefficients are all very similar between these two modules. When mixing modules on an array, please try to make Voc of your strings as close as possible and the inverter will run fine. The inverter’s MPP tracking algorithm looks at the array as a whole and will make a few compromises if the array is not completely uniform. That being said, these two modules are so similar you will likely not see a loss in performance compared to an array of one module make and model. You may even see an output advantage due to the extra current available from the Hanwha 235’s".

Yes, it is possible.Yes there will be performance degradation from mixing modules. It would be difficult to quantize the amount of degradation, particularly on closely matched modules, and it would change with time as the array ages and the modules degrade.  
If you build this system the inverter will operate, energy will be produced. If you happen to have a good deal on these modules and it would be much more expensive to swap out one of the module types for the other then maybe over all you will end up ahead. Don't expect to be able to prove any particular outcome though.