Help about sizing ELC STAR SPORTSWEAR before buying 44 or 46 ? I'm a 44R with "common" jackets

[bn1966]

Began with a size 46 ELC A-2 which looked great undone and was a pig to break in, chose a 46 because that is my chest size. Gave up in the end and purchased two 48’s (Monarch & 50 Cal) which look fine undone but can also be zipped up without breathing restrictions