I manufactured a 2.5" mandel bent stainless cat back exhaust for myself and I have a Magnaflow stainless muffler on the end.
It fit just fine as there is piles of room under the Optra.
I will say that it is fairly loud.... at first I had a flowmaster muffler on the car and it was so loud it made my ears go funny. ( felt disorientated )
The last time I had that sensation was when I pushed 144db at a local stereo competition.
The Magnaflow muffler was more money but it's way quieter and it has less restriction than the Flowmaster.
Needless to say it's still very raspy at certain RPM so I'd suggest smaller piping such as 2" for Naturally aspirated vehicles.
The only reason I went with 2.5" was due to the fact that I will be installing a turbo system very soon ( If Fed-Ex ever finds my turbo

)
I don't have a resonator either.... the current system is probably 30lbs to 40lbs lighter than the stock system as the stock muffler and resonator are very heavy.