I remember you have a plan to burn many discs at low speed. I don't think the quality improves so much just by reducing the burning speed. In my experience, once I have a good media at, for example, 12x, then 8x or 4x burn is virtually the same (That's why I settled @12x burn for TY T02).
Here are my (value line) TYG01 discs from supermediastore. The first is @4x, the second is @8x (I had to use G02 strategy to overspeed it). These two are close to the best burns; i. e. they are pretty good, but not as good as the best TY can be. As you see, they are not so different, and indeed quality difference between discs were much more important than the difference between 4x and 8x.
I realized that @12x its quality drops, so I settled at 8x burn. (Yeah.. I asked too much for 4x media.)
My final remark is that, 16x writer producers doesn't make too much effort in low speed burns such as 4x and 2.4x. The same story applies for the media maker. You may even see quality drops at low speed.