HP P410 works fine, i used it on my build with the 512MB and battery backed cache, also used a HP P400 and the standard LSI controller...all worked with my SAS 15K HDD's.
There was no need to buy backplates if you studied the standard backplate design and the cpu cooler retention system, mine was pretty much plug and play just didn't' have to install the standard plastic backplate worst case scenario you would have to use different screws because of the thread.
If the heatskink is getting hot is actually a good thing, it shows that there is good thermal conductivity between the chips and the heatsink, problem with that piece is that those 2 chip's have a TDP of 27W each.... http://ark.intel.com/products/36783/Intel-5520-IO-Hub
There was no need to buy backplates if you studied the standard backplate design and the cpu cooler retention system, mine was pretty much plug and play just didn't' have to install the standard plastic backplate worst case scenario you would have to use different screws because of the thread.
If the heatskink is getting hot is actually a good thing, it shows that there is good thermal conductivity between the chips and the heatsink, problem with that piece is that those 2 chip's have a TDP of 27W each.... http://ark.intel.com/products/36783/Intel-5520-IO-Hub