I would just install a PCIe USB card with internal ports. If you want to boot from it (i.e. ESXi), you may have to find a card that has a BIOS insert for boot capability. There's a good chance the Dell BIOS will see it natively and boot from it regardless.

If you *are* planning to boot ESXi from this internal USB drive, I would recommend an internal SD card reader. There are several reasons, but the most obvious is that Dell and VMware both suuport, and approve, of the format for that purpose. You can even order a lot of PowerEdge servers with the reader installed.

I too was interested if upgrading the side plane would enable Gen I and Gen II 2950's to use the internal USB port so I ordered a card. While the card does work, the BIOS doesn't have an option to enable the Internal USB port (as described in the 2950 Information Update). I tried connecting a USB flash drive anyway, but the system would not recognize that it was attached.

For reference, I was looking to load ESXi on the USB flash drive and I didn't want it sticking out too far from the back of the rack and risk having it knocked out of the USB port, so ended up going with the SanDisk Cruzer fit which have about 1/2" depth and just connected them to a back USB port.