There is no reason why you couldn't try for example 100, 110, or 120 mm stem. If anything, I would guess that having that longer stem makes handling more stable, which isn't a bad thing especially in a tri/tt bike. Remember that 40 mm (more reach) is roughly equivalent to two frame sizes, so you have plenty of adjustability. That's the beauty of those non integrated cockpits...
(Fwiw I would try a 120 mm stem and if that's already too long, you'd anyway have the chance to move the armpads rearwards.)
(Fwiw I would try a 120 mm stem and if that's already too long, you'd anyway have the chance to move the armpads rearwards.)