Ba***dising a larder unit for double oven - Retrofit

Hi all you lovely Forumites - here's a challenge...,

I am trying to convert a 600mm larder unit into an double oven housing. I 'think' I have the correct cavity size: width seems correct but depth, once the backing is removed, is a mere 560mm. The appliance mins are 550mm. Is this fine to fit with only 10mm from the brick wall that remains?

Also, I will need to retrofit a shelf to support the 49kg of the appliance. I can't get access to the outside of the unit to use cams, and so will have...

Ba***dising a larder unit for double oven - Retrofit