The Lenovo P350 case is slightly different than the other Lenovo Tinys I've been using, and I had to model this one from scratch. It won't, for example, work on a M720q without modification.

The screw holes are threaded, and you can reuse the original screws with PLA. On a Creality CR6-SE at 0.28mm, it's not perfect, but it is good enough. With a small effort and a hand driver, the screws will self-tap the rest of the way, and torque to a reasonably snug level. You'd probably have to run a tap or have a high resolution print for anything tougher than that, though. Or just drill out and use your own hardware, as is the case with most of these types of brackets.

I printed with the arms that mount to the adapter in the up position, with supports.

If you remix, please share alike.