Quote Originally Posted by AlexG View Post
...Although it's miniscule, the slight variation in the height is enough to throw the focus off...
Are you sure? With a well-aligned enlarger and apertures of f/5.6 or smaller, you have at least 20 mm of depth of field at the base board with an 8x10 print, more with larger prints. An 11x14 print from MF at f/8 has 30 mm DoF. Use a sticky tape for optimal sharpness, but I doubt you really need it.