I have two of them.
A year or so ago, I made that same mod to one, although slightly better done. More solidly built, with the slot at the top side of the gearbox as not to weaken the piston rack. The pisyon in mine was fully connected to the faux bolt and didnt have to rely on the forward thrust of the whimpy bolt spring.
I ended up taking it out eventually. It got annoying after a while really, and I thought it was kind of cheesey with the bolt only moving halfway back.