In considering the bar stud mounting, you may only increase the width by half an inch or so. You will still need some sort glide plate in there to not just go against the side of the wood, but to also support the whole rack (remember, the studs would be on the bottom of the saw when milling, and on the Alaskan the rack slides over the log above the bar). Also, when clamped to the studs, if you are also connected at the bar tip somehow then you won't be able to easily adjust the chain tension without also either adjusting the connecting point at the bar tip or by extending the width of the whole mill.
@BobL on his big mill has a stud mount, but he also has custom chain-tensioner out on the bar tip. Its a really cool set-up, but probably only worth doing on a big mill and a big saw (his 880 also has an inboard clutch, so he can remove the clutch cover to clamp on the studs)
Though, if you use the "Small Log Mill" by Granberg, there is only a connection on the engine side, not at the tip, so you can get more cut width with this, but also less support and more chance for an uneven cut.
I have the "Small mill" by Granberg and on my 20" bar I made my own nose clamp set-up. Just used some angle iron, a u-bolt, and put a 6mm (1/4") screw through the sprocket center to maximize the width (instead of clamping on the bar, which would be done below the tip sprocket). This stabilizes the bar much better than the single clamp, and gives an extra inch+ instead of clamping on the bar tip.
I have seen set-ups with a stud mount where the saw slides on fixed rails that are below the log, but this isn't quite an Alaskan style mill and more of what is done by Logosol. You may want to look for some home-made Logosol-style mills if looking to do stud mount.