Are these strictly "ornamental" as in an architectural or furniture application?
Or are there specific functional dimensions and tolerances that must also apply?
Also, you mention the part is 1/2" wide and .1" thick.
Then you state that putting a "There is also a 45 degree bevel" on the back reduces the width down to less than 1/4" wide (".240"x27" contact left on back side. So you lose approximately 50% of the contact area after bevel")
It is not possible to put a .260" wide 45° bevel on a piece that is only .1" thick. The most would be .1" wide (reduction of back width). Are you beveling both edges? That would leave a flat .300" wide if both bevels go to a knife edge.
Most 42" table mills have 30" travel, but that is not how I'd do it. A surface grinder sounds the best solution, and less dressing of the wheel on a 10/12/or 14" wheel machine. As others mention, the material will curl. But it would probably curl more off the milling machine. I could grind it or plane it with the travels on my machines except that I don't currently have a 30" chuck. 1030 grinders are pretty common; but like mine, many don't actually have full length chucks mounted. I've got a 10 x 24 chuck mounted on the 32" travel grinder. On the planer, to do strips those dimensions "conveniently" i would also use a mag chuck with a stop at one end. My longest chuck for the planer is only 18".
For a vertical mill with the head tilted, the work would have to be fixtured to constrain is side-ways as well as to keep it from lifting. For a horizontal, it would still need some sideways constraint. With conventional cut, there would need to be something to hold the work down. Though with a one pass climb cut it might be possible to mill the shallow arc with only some sideways restraint. All milling options consider over length blanks and sacrificial ends to be cut off later. Or else a dedicated fixture. Or move hold-downs sequentially as the cut progresses.
smt