The simplest way to fake out Flite with an alternate pronunciation, if you have the luxury of knowing the words needed in advance, is to have Flite say a series of single-syllable words with the phonemes you actually want. I did this many times in AllEars because the Flite voice I chose didn’t say email, iPhone or mobile in a way that I expected to be immediately clear to the user. So instead I gave it @”eem ale”, @”eye phone”, @”moe bile” which worked out pretty well. Is that kind of workaround an option for you?