Ugly is a matter of personal taste. 3"- 5" is standard crown, but I have double crown moldings that extend to 9-1/2" that look great in a room with 8' ceilings.

It's not neccessarily too large for an 8' room, but will it be in scale with the remainder fo the trim in the room?

Even if it is not in scale, that may not matter depending on the amount of existing trim and the combined sightlines of the room.

Mongo

To be honest, even my wife thinks its kinda garish and oversized for the room. I just want to use the stuff! It would be a shame to take the loss on such beautiful crown molding!

How do I tell the sightlines and scale to make the moldings fit and look natural?

Go ahead and nail some it up and look at it in place. If it looks good to you after a week then do a permanent installation. If not then take it down and sell it. If you can, include an outside corner in your test because crown is most noticeable at outside corners.

As far as scale, crown that size should be matched with 71/2" base and 4" case in round numbers. The window trim will look better if it includes stool and apron. But, that's not a worry until you see if you like it on your ceiling.

Jan

What is a stool and apron for the window trim?

The stool is the window sill, the apron is moulding or trim that extends down, below the stool.