Wrapping G.O.M. around light tray corner?

Does anyone have experience with fabric techinques for covering G.O.M. around 90 degree corners? In my new theater I plan on wrapping the MDF soffit light tray with G.O.M. to finish it.

Here is a google sketchup of one corner:


Heres a picture of the actual corner ready for G.O.M. covering.



Here is a sketchup of the MDF tray with both 90 degree bends.



Any techinques would be most appreciated.

Thanks!

Thanks Bud for the pic and reply. No I am not planning on the 1" Linacoustic on the bottom of the soffit. Based on my calculations the underside of the soffit extends only about 8" from the front of the speakers which I hope will cause any first reflections to occur well in front of the seating. This decision is also due to the P.I.T.A. factor of getting the Linacoustic on the bottom of the soffits as well. Same with the entry wall and closet walls.

I am thinking that I might just go with quarter round on the inside 90 degree vertical corners. I will probably start with the fabric on the bottom and wrap them up, cutting the fabric at the 90 degree joints and cover the cuts with quarter round that is painted the same red as the GOM. Yet to figure out is the technique for getting a clean seam on the door entry wall. I hear that thin cardboard strips stapeled in from underneath and then the fabric stretched over itself hides the stapes and produces a clean edge. All other walls fortunately will have the 1" panels to hide the rough staple edge.

Thanks for your replies.