Stage 1: Optional Criteria 2 Doubt?

2) How do I demonstrate that I have been recognised for my work outside of my immediate occupation that contributed to the advancement of the sector?

I two have 2 evidence where I was working outside my company with other 2 companies as an engineer on a contract basis. I have contributed to their core development and I do have a reference letter from their head/managers. Can I submit 2 pieces of evidence as I have been recognised for my work outside of my immediate occupation that contributed to the advancement of the sector? is it valid to add that in OC2 or should I add it in OC3.