How Thick is your flat Earth?
I don't think anyone knows. Some say its infinite, other a few thousand miles. Not sure what Rowbotham said.
So if I dig a hole I can't pop out the other side and meet an upsidedowner 
That would be interesting if you actually digged yourself through. What would happend if you jumped through
the hole?? Would the earth accelerate away from you (upwards), or would you just be flying in the air?