Anyway, the subfloor is now solid to avoid any mortar or grout cracking. Or at least, I hope it is! I actually used a special mortar that applies to wood bases and will supposedly allow for some flexing.
Here's a little pictoral tour of this latest endeavor...
With old floor:
With new 1/4" plywood covering subfloor:
Applying thin set mortar (special to wood subfloor) and installing tiles:
The finshed product: