A bit of an update: The waki sheath fit way too tight, because I formed it to the bare blade without anything wrapped around it, and I did a really tight fit with the foam press.

So, to loosen it up, last night I wrapped the blade in tape and then heated the sheath with a hair dryer and forced the tape-wrapped blade in. After a lot of grunting and swearing this morning, I was able to extract the waki, and remove the tape. The fit now is MUCH better. I will probably have to tighten up the guard area for a little bit better retention, but overall I'm very pleased with how it turned out.