As a player who flew the Obstinate/Adamant (Same shet tbh), I can confirm this thing is obnoxiously large for it's capable firepower.
The way I see it? There's two solutions to this.
Squish obstinate to resemble something like hasta, still should be bigger in at least 0.5x size, as then it would look retarded OR downscale it overall.
2nd solution would be to give it the firepower of a medium battlecruiser, personally I'd go with this. (Just my opinion as a player who enjoys going for eachother's necks, literally)
Obstinate as it is is way too big for a 2-heavy wielding battlecruiser. While as far as I know all battlecruisers have the same powercore and turn rate, their armor differs and their armament as well. The HP is ok for a light battlecruiser, but it needs light battlecruiser shapes as well. Or if its easier work for devs, rather than downscale it, as I said, you can also add a third heavy slot and maybe buff the health, to resemble a medium battlecruiser.
Imo any other BC or average flown BS will eat it alive with ease in it's current state.