Offsetting twin RSJs to lengthen the beam

[MaxA]

I am installing a twin steel beam to support a chimney stack. 
The beams are 125mm too short. I'd rather not order new beams as these were very expensive and massively over engineered for the job.

My private building control inspector has informed me that I can offset the two steels to gain 125mm and connect them with 3 tube connections. 

Can anyone confirm that this is right and safe? Sketch attached 

 

The alternative would be to add a splice but this would cost around £300 and again seems like overkill.

 

Thanks very much  

[nod]

I would check with your SE 

Quick phone call