Making a voice sound smooth instead of choppy

[chrisj]

I have Textaloud and I downloaded a sample of Cepstral Allison.

Then I asked this on the TextAloud forum:
"It sounds smooth when she says "please register me", but the additional lines of text I've added, as a test, sound choppy (maybe you could tell me the correct term, instead of choppy). I could send you a sample file to hear if you'd like. How can I make my additional lines sound less choppy?"

The reply was:
"It appears that Cepstral voices are based on some statistical models so it may sometimes happen that a specific input comes out sort of choppy a little. However, there might be some likelihood that one day Cepstral would introduce additional corrections to speech units and improvements to source waveforms, which would hopefully result in smoother synthesis with Allison, as it happened to Callie a while ago, for instance."

Does this reply mean there is no way to make my additional lines of text for Allison ever sound smooth? Isn't there some teaking that can adjust this?
Obviously, I am very new at Text-to-speech, so any assitance would be greatly appreciated. Thanks.