Ahm, but I use Photoshop CS 3 and it makes my highlights layer completelly dull o_o;
Oh, oh! I was able to merge down the layer without losing the highlights, by doing what you said, using layer clip first. I didn't lose the highlights. But if I have a multiply layer on top on my normal layer, and then the addition layer on top of those, layer clip doesn't work (because I would have to use it with the layer directly below it). And I was able to make it work before on this other drawing, but I don't remember how I did it. Now I opened it in SAI again, modified a small detail so I could save over it, and bam, when I open this newly re-saved version in photoshop CS, I lost all my highlights. It's weird, I just wish so badly I remembered how I made it work before!! ><
But at least there is a sort of workaround, I just have to make sure to be able to use layer clip and have no layer between the addition and the normal layer...