Two 2 inch by 2 inch both 1/2 inch thick top and bottom correct? And this for 4 diodes such as 44 and 06 running 4.5 amps each?
If so it would get too hot in under 2 minutes, and as warm as you would ever want it to get in about 1 minute. Estimated.
That's about the amount of mass and surface area, well a bit less actually than I run 1 nubm44 in for 5 minutes.
4.5 amps at 4.7 volts in to each diode is 21.15 watts into each diode to get 7 watts out before the lens, so 56 to 60 watts of heat with lens waste and drive heat or a solid 55 watts of heat just in diode by product.
Imagine 11 x 5 watt lasers all pointed at your heatsink without any energy reflected, that sucker is going to get hot fast.
On top of your plates you need some thermally bonded fins and a small fan blowing across them.
Here's two 2 x 3 x 1/2 plates attached to a 1/4 inch plate with some small fins and just 1 nubm44 gets this hot in 5 minutes.
The reason is these diodes are much more efficient at factory spec of 3amps? but at 4.5 they lose efficiency.
These nubm44 and a nubm08 run for 4 to 6 minutes before they are getting good and warm, but that's 1 diode each, the small is a 2 inch wide round bar 2 inches long the large is 2.5 by 2 and that adds 2 minutes but it's a 4.0 amp nubm08 and the long is a 2x2 round bar with a 2.5 OD 1/4 wall sleeve 6 inches long and has a 6X pair, it's good for a solid 5 minutes but it gets hot after that except during winter I can run longer, the heat just keeps building up without forced air and surface area multipliers such as fins.
I had 3 NDB7875's in a 2.5 x 2 inch round bar all at 2.4 amps each and it was really hot in 2.5 minutes or so.
Multiple overdriven diodes are going to make a lot of by product heat, just mass alone won't give extended duty cycles, not reasonable mass, not for multiple diodes.
