There's still plenty of elbow room in there if you want to taper the elbow and upper arm a little bit. You can still taper the upper arm and avoid the armpit area if you're worried about that. Also, don't worry about your biceps becoming too big for that hauberk. You'd quite literally need to have world-class biceps and triceps (triceps actually make up 2/3 of the mass of your arms) that are Mr. Olympia worthy for you not to fit in that. And if you want to become an IFBB pro body builder, you're many years, and many steroid injections away from worrying about not fitting in your hauberk sleeves
With the elbow, bend your arm all the way, is it pulling tight at the elbow? If there's still room in there, you've got room to taper, which I suspect you do.
Even with the tapering you've done, it looks a thousand times better than the standard tube sleeves. It looks really good with the helm and mace as well!