I'm trying to assess whether the PowerEdge R640 would be a good fit for my organisation, and while doing so I have a question regarding the hardware configuration.

The R640 with a PERC H730P Minicard controller and 4 3.5" drive bays seems like it would be a good fit, however it would be ideal if it were possible to fit two SSDs in there and still have those 3.5" bays available. For this exact situation, there seems to be a 'Dual 2.5" Rear Mounted Flex Bay' available, which looks promising. Additionally, according to the documentation, the PERC H730P supports up to eight internal ports and from what I can find there indeed should be two HD Mini SAS connectors available from the H730P Minicard.

Now my question is: Since the main backplane should only require one such connector for the four bays, would it be possible to use the other connector for the rear drive backplane, and that way connect both the main backplane (with the four 3.5" bays) and the rear backplane (with the two 2.5" bays) to the PERC?