Hey all, just wanted to send this along.
I've got 4 of the M90q Gen3 65w i5-12500's with x16 risers and have added the Dell branded Mellanox Connectx-4 LX cards to mine.
Initially they were just floating around the back but decided to have my hand at modifying a 3D model someone made for a different card to see if I could make one compatible with these.
The result is a fully functional baffle that holds the card firmly without any clearance issues and also uses the original screws from both the card, and the chassis.
Here you go.
Lenovo M90q Gen3 ConnectX-4 LX (Dell CX4121C) Dual 25G Baffle Remixed by Chewza
I went with a similar solution for the X550, But I'm using USB to power the fan (The Fan is mounted with a little PCB standoff):
The USB connecter barely fits through the hole next to the ethernet port.