I bought my GS300 in January and I also had the bad dash creak. I got some black rubber for sealing the inside of double glazing and pushed it down between the dash and windscreen, made a big difference. Last weekend I took out the radio/nav screen and lined it all with the fluffy side of self adhesive black velcro, easy enough and very effective. It is always worse when cold because the plastic is harder. There's a YouTube video of the procedure. If you decide to do it he shows 2 screws being removed but there are actually 4 as I discovered when I couldn't initially budge it! Well worth the effort, I went out this morning in minus 4 and no creak!