Standard Citoris, to include the Ultralights, have a conventional inertia trigger system. It’s proven and works very well, particularly in such a light gun as the ultralight.
It’s the 725 that has a mechanical trigger. Well, I should say that the 725’s trigger behaves mechanically when dry firing, but still has a (very light) inertia block that must be kicked to the rear to reset the trigger; this is done by recoil and is theoretically assisted by a kicker attached to the very rear of the receiver with is pivoted upward by a fat coil in the hammer spring, thus cammimg the inertia block to the rear….usually. Problems can arise with very light 12ga loads and/or particularly with 28ga tubes, as the slight amount of recoil seems to somehow counter the effect of the kicker. It’s really weird.
Someone could easily make a heavy inertia block for the 725 that enables the removal of the kicker and other weird “mechanical” aspects of the trigger system. Problem is, the 725 trigger system has been heavily revised at least twice, to include even a top receiver tang that is taller at the rear for the tensile purpose of more vertical space inside the receiver for the dubious mechanical trigger components—meaning, it would take way too much reverse engineering R&D by an aftermarket source to make such a part for every known 725 variant. It’s just better to not go there, which is why I killed the idea of pursuing this endeavor.