Should point out - I'm 6ft, and 11st 5 ish - so average height but quite scrawny - and it felt like I was wearing a tent with half-mast sleeves!
I, OTOH, an 5'8", 11st 3 ish and stocky, and the last few things I've tried just don't fit me either. M is too short (this in tops btw, and I'm fairly long in the trunk with wee legs) and L is the right length but assumes I eat a dozen lard pies a day (and while I'm not fat I'm certainly not skinny). That was a Quito jacket, Torres gilet and Fuera smock, all rejected despite money burning hole in pocket all ready to buy them.
There again I have a couple of their reversible shirts (L) which fit me very well. It's just the outer layers that don't seem to work for me.
So, try before you buy definitely seconded.
Pete.