I don't recommend the use of older hardware, because older hardware is likely to be closer to the point of failure, and even solid state electronics will eventually suffer age-related failures. I also don't recommend the use of hardware with installation
issues of any sort. In this case, "known issue" reads as shorthand for "yeah, we know the BIOS is broken, so here's a really inconvenient workaround instead of fixing what's wrong", not something I would consider acceptable.
That said, however, just install with a single DIMM, then add the additional memory. It's just like any other version of Windows in this regard.
I'm not on the WHS team, I just post a lot. :)