yes sure, the clip when you find the good way to place it, after it work very well, then you could also use others plug for SOP. Wait I found the box where mine is, I will show you.
EDIT: I see you want to test Coreboot. Which is the bios ship model that you would like to flash ?
REDIT: I checked your tuto, is well done. The ship bios on the T420 is the Winbond W25Q64CV
They said:
supply Voltage 2.7V to 3.6V
W25Q64CV Publication Release Date:May 22, 2014-5-Revision H1.GENERAL DESCRIPTIONThe W25Q64CV(64M-bit)Serial Flash memoryprovidesa storage solution for systems with limited space, pins and power. The 25Qseries offers flexibility and performance well beyond ordinary Serial Flash devices. They are ideal for code shadowing to RAM,executing code directly from Dual/Quad SPI(XIP)andstoring voice, text and data. The device operateson a single 2.7V to 3.6V power supply with current consumption as low as 4mAactive and 1μA for power-down.