So... I'm comparing this to a M720Q in front of me, and based on where the rear lid screen goes, it looks like the current design might just fit, it may interfere with the screw between the heatsinks, but not much modifications would be needed if I had to guess. It actually looks like the M720Q actually has the fan and shroud closer to the card than M90q Gen 2.
I also have an M70q, it has a very similar design to that M90q, but the heat sink bracket seems to be different.
Two things I notice, on the m70q, the screw for the heatsink bracket is in a different spot, probably because the M90q uses a two piece heatsink shroud, while the M70q uses a one piece. So, I believe your screw in set in the place where I've circled it on my M70q. If that's the case, I should be able to mock one up soon.
View attachment 37565
If I can get a pic of the P350, I'll see what can be done.