Leather Jackets: Post Pictures of the Best You've Seen/Owned? - Page 537
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5'10 @ 39chest is not a large 48, it's more of a true to size 48/slim 48, the 46 should be bang on fit.
The jacket looks roomy for you in the chest area, but that is how it should fit, if you want it snug, 44 would be your best friend.
Based off measurements the 46 hasn't changed at all in terms of size this season. You maybe could size down to a 44 to try? let it stretch.
If you want to layer something underneath, pretty much perfect size you got there I think.