I just set VstSynthFont as default and that will load the JJazzLab font. I think I had to type the name in the soundfont browser in VstSynthFont as is was not showing the directories properly.
That threw me for a short while. I had presumed that VSTSynthFont (and SynthFont1/2) were sound-fonts, like it kind-of says on the tin, but it isn't ... it's a sound-font player.
I found the same when I looked at TinySoundFont for something in which I wanted a very compact sound-font. It's not a sound-font.
"How absolute the knave is." :-D