The carrier board in that link does look like the Sintech-C I use. Rocket 4 Plus 1TB is single sided, however, so I couldn't speak to double sided compatibility. I think larger capacity ones are double sided.Did you find the Sintech-C adaptor a hard fit to hold a double sided SSD? Sintech on Amazon seems to indicate it's a problem for the Sintech-D adaptor which I think is just the C adaptor plus tools. It's in the description plus in one of the photos. They say nothing on Sintech's site though. https://www.amazon.com/Sintech-Compatible-2013-2017-PRO(Late-2013-2015/dp/B08JTDLMXJ/ref=sr_1_1?dchild=1&keywords=ST-NGFF2013-D&qid=1613161137&sr=8-1
I've yet to commit my order for that drive plus adaptor but getting close. Did you ever note power consumption when benchmarking? My guess is that if the power management of the SSD firmware is well tuned, you should come in lower than other SSD's when running PCIe3.0 or 2.0, as the chip is fabbed on 12nm FinFet and descriptions on Sabrents site indicates need a heatsink if on PCIe4.0 and they say nothing otherwise.
Re fit, I did buy the Sabrent heat sink and it's way too big to fit in the Mac Pro 6,1 - you can't put the case back on. The drive gets really hot to the touch during use, however, so I think it needs one.
Without a heatsink I was able to screw both carrier board and blade in. With a heatsink, however, I just screw the carrier board in and use the silicon straps that came with the thin heatsink I bought to secure the heatsink-blade-carrier board sandwich all together:
2 Pack PCIe NVMe M.2 SSD Heatsinks Cooler with Nano Silicone Thermal Pad
2 Pack PCIe NVMe M.2 SSD Heatsinks Cooler with Nano Silicone Thermal Pad
www.amazon.com
I'd really prefer a heatsink with a fan, but think I'd have to use the magnet trick to run without a case for that, or find power for it from the screws in the top right corner of the board some other adapters like the AngelShark use. I do have big fans above and below the Mac Pro itself, so it is basically a big wind tunnel at this point, at least.