Love this fascination with TOA's... Some people's beliefs in the benefits of a low TOA borders on fanaticism.
Anyway, first off, does the Fireup 99 make the antenna physically longer? If it doesn't then your take off angle will not be lower. Unless they achieved the shortening via a top hat, which it clearly states in the advertising that they didn't.
Further, even if it did extend the overall length to a full 5/8 wavelength, I think the difference in take off angle from such a gain is much smaller then you seem to think. Most of this is actually dependent on ground quality of the earth underneath the antenna and height above said earth.
The DB