F&G addressable loop more than 3 km

Dear sir/Madam,
We designed an addressable F&G system with SCAME (S 81) for a Cable Gallery (like a tunnel) with a 2 km length. Although the loop length is 4 km, the first F&G devices have been installed after 1 km (It means we installed detectors on the 2 km of the loop only).
Since there is a limitation of 3 km for an addressable loop, please guide us to a solution for using this system without relocating the F&G panel.
Your familiarity of the situation did not translate well into the description you provided, as evidenced by no answers in over a week.

I can only speak for myself, but I can not make sense of all the length dimensions you're talking about: 1km here, 2km there, 3 km here, 4 km there. I would recommend you make up a labeled sketch of what the layout is, what the layout needs to be, and what limitation amounts to, what is a 3km addressable loop? 1.5km out and 1.5km back for a single point? Maybe someone can help you out if your situation is described graphically.
As you know a loop means round to go and return. Now, there is an F&G addressable loop with 2km go and 2 km return while the first detector is installed after 1 km of the start point of the loop from the panel (It means 1 km of the first part of the loop has not any detector). Since the manufacturer say we can not use the F&G loop more than 3 km (I'm not sure) could you guide me to how I can use this loop without relocating the F&G panel or shortening this loop?