Plexiglass and acrylic are basically the same thing. Your windows are being held with rivets. The gauge of plexiglass used however is quite thin. Seems likes a 3mm glass, hence the warping.
@N2O It would be best to stay with your current front and rear shields. In case of an accident (Allah forbid) plexiglass would break into large chunks which could potentially add to the injuries while the factory screens break into small pieces, reducing the chances of injury. Saving a little weight, hardly 8-10 kg and putting your life at risk in doing so should be a no no. Plus, the plexiglass / acrylic is prone to getting lots of swirls marks, even when sliding your hand over it with dust on the surface and its starts developing very small cracks when exposed to sunlight which would seriously hinder with the visibility.