Not sure how much this helps, but I wear a small in the shawl fisherman and a 38 in the shawl heirloom. Also interested in more info about the heirloom crew neck. How do they fit? Photos, of course, would be great.
I'm 6' and wear a 38, which is correct for my chest, and the heirloom has a good fit on me, falling at my waist. For reference, I wear a regular length jacket pretty much everything, including Epaulet x Southwick items, and wear a 31"-32" inseam. If the heirloom fit one inch longer, I wouldn't mind; it would just be a bit more traditional and less fitted. Hope that helps!
Hmm my experience with GBV is different all around, as often different GBV shirts have different fits from other GBV shirts year over year, or even within seasons. The one GBV shirt I have fits slightly slimmer than EP, but I take the same fit anyway. And just to be clear that "Epaulet by Gitman" and "Epaulet by New England" have the same standard Epaulet fit. GBV is its own thing from Gitman. Blackwatch was a very dark forest green ground with a brighter light green...
In addition to laundering clothing, I also wear clothing.
Old stuff on Rapeleye Street after a long day:
LBM 1911 navy linen SC, from EP
Ashland (Gitman) lavender chambray shirt
Juniper Italian linen Walts
Not pictured: Carmina x EP caramel double monk straps
Not EP: Vanda green linen houndstooth tie & silk PS