Seen it done on a 757 subject to the attentions of a Boeing team after a hard landing @ Funchal. Hard landing? Nose gear torque box change. Flt deck floor was level with galley 1. Anyway, they had the aircraft levelled and installed an IRU with rack on a floor beam in the centre of the cabin (floor was up). Rack was supplied with extension cable to the E/E bay. Calibrated by PFM but all worked OK. E/E rack had been pushed up to keep the torque box company.