I'm not sure if you're still having problems with this, but another solution is to increase the resolution of your ray trace. Go to ray trace assistant, check off interior & high quality and then click next. On the next page, check off 'units' instead of 'pixels' next to dimensions. Next change your resolution from 72 to something higher. I use 300 for very high quality renderings, but 150 also works very well. Make sure the width and height remain at the size you want them at. If you try to change the resolution before switching from 'pixels' to 'units' it will make your drawing size very small. Please note: the higher the resolution, the longer the ray trace will take to complete (especially if there are a lot of reflective surfaces and/or lights). This, along with allowing for multiple passes to complete, will help increase the quality of your renderings.