I do 38R for Zegnas but everyone here screams at me for wearing one size too small. My waist size is 30/31. If the Formosa is cut traditionally and not tapered then I believe I should go with 38R. I will have shoulders and etc measured today and see where I fit. But looking at the pants size for 40R, it was like 34~36. That means I would have to do mad alterations on them.
Hi M - I replied to your PM. Traditional vs "tapered" isn't really a useful terminology for suit/jacket cuts - unless you're referring to the trousers only here?
Secondly, most people do not know the measurements of their trousers - that's a proven fact after hundreds and hundreds of customer service Q&A. That's not to say you don't (you may) but it's better to check. Take trousers that fit you well, lay them flat on a table, buttoned, with the waistband completely flat (not curved), and measure it from end to end. Multiply by two - that's your reference point