Without knowing the detail of the case, if is impossible to advise. You would need to give a breakdown of all the figures and some background re children and any other specific needs or issues.
What did the judge at FDR have to say about the proposals that were put forward? It is rare for a final hearing to deviate far from the view of the judge at FDR.
Is there a reason to depart from 50:50??
Have you had any legal advice??