Hi all. I saw now the 750m ultra bay is available in Lenovo website. It is for the 15'' like y510p. After some research, I found that for 650m version, the GN36(15'') can be fitted in Y400, just some change on the adapter. (Resource:关于Y400安装GN36显卡的问题_笔记本吧_百度贴吧 Though is in Chinese). So I think it should be possible to fit 750m in y400or y410p. But I don't know if the bios of these two supports SLI or not.