Tall single doors are much more prone to warpage. Many cabinet manufacturers will not warrant a door taller than 42. With 108"ceilings, you have 54" of room to play with. 6" of molding would be proportionate.
That leaves 48" for cabinets. You can do 30"+18"; 33"+15"; or 36"+12". 12" is too small for glass doors if you want that. 33"+15" would be ideal, but is an odd size that many cabinet lines won't support. 30"+18" is easily done in any cabinet line and aligns well with tall cabinet heights, so the overall effect is seamless.
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