Soft T and D sounds in an English voice - Newbie

[htayal]

Hi,

I'm using Acepela Deepa22 voice for Indian English. I'm having trouble getting this voice to pronounce soft D/T sounds. My purpose for buying Textaloud will be partially defeated if I'm unable to do this. I tried to add an entry into the dictionary but couldn't figure out a way to add soft sounds.
Any ideas?

Thanks.
Himanshu