Can I build an expanding arbor?

I wish to build a cedar garden arbor that is 4' wide at the rear and 5' wide in the front. It will be used as an entrance to a vegetable garden from a flower garden in the corner of our lot. The corner shape is similar to a baseball field with the entrance in center field. I believe an arbor that angles outward would look better than a traditional rectangular one. If I angle the base posts I should be able attach the first set of top planks along the sides of the base posts and they will be flush. From there I should be able to make angled cuts in the bottom of the 2nd set of planks so they smoothly slot on top the first set of planks. The top row would be spindles angling outward from the rear of the arbor towards the front. Can anyone think of a reason that this plan would not work? I do not have any arbor building experience, but then I have had limited experience on a host of other jobs around the house and have completed them correctly. Thanks!