I work in a company where we are able to work from home. However, each department is able to come up with the proportion of WFH/Office days. Many are 1 day in the office. Our department has decided (senior management) to come in 3 days in the office. I would like to apply for 2 days in the office/3 days at home split (with a 3rd day as needed - I am already flexible and come into the office for meetings on my WFH days - they are equally flexible and can WFH on my office days if something comes up but this means needing to justify it). I have done an analysis of my calendar since January where it seems that on my days in the office I am on average having 2hrs of face to face meetings (mostly 121s with my manager/team/team meetings). I think this is clear that there is 'no need' for me to be in the office 3 days. Any help in terms of the justification (we need to say how this will affect the business in our form).
Also any advice as to whether to go informal first, or formal immediately (my manager is not that fussed I think - but the director is who wants 3 days in the office, because they say that we need to be present).