"Randy" wrote in message

Can somone who has a Porter Cable 7518, mounted in one of the fancy new
lifters, measure the height, and let me know what it is.

It is the same height in the lifter as out. The router does not change.

As for how much clearance below the top surface, it will be the router
height with bit in place and lowered to the most shallow working position
for that bit. The mechanism of the lift may or may not protrude below the
router. That is brand specific.

I'm designing a new router table, and though I don't own them yet, I want
to design the table to fit them for the future.

You'd be best off to get the measurements of a couple of brands. My router
is 9" below, but the Benchdog lift is about 10 1/2"
Ed