[U-Boot] Dumb question: is UMS/MASS_STORAGE_GADGET in SPL possible?

I'm trying to make a small image enabling u-boot UMS mode on BeagleBone Black against the on-board eMMC. Is it possible to enable UMS simply within SPL?

It seems like some others have done it in the past ( http://lists.denx.de/pipermail/u-boot/2015-March/207600.html), but I don't see an obvious way to enable it.

Performance might not be great ( https://boundarydevices.com/u-boot-usb-mass-storage-gadget/), but minimizing the user steps could make it worth doing it in u-boot (preferably SPL) than to load a kernel and ramdisk ( https://github.com/ungureanuvladvictor/BBBlfs).