[Closed] Will a 1 3/16" adjustable reamer adjust to 30.9mm ?

I've got a 29.8mm stoker stem for the tandem that I want to fit to a 30.9mm seatpost.
Now, I know the obvious answer is to buy a 29.8mm stem and a shim and I know that removing metal from the stem will weaken it and invalidate the warranty, but let's assume I want to have everything the same size and not use a shim.

There's a cheap 1 1/16" to 1 3/16" adjustable reamer on ebay at the moment.
1 3/16" is 30.1625, which is 0.7375mm smaller than I want.
How exact are adjustable reamer specifications ?
There must be some tolerance and they must err on the outside of their upper and lower limits, but by nearly 0.75mm ? Am I expecting too much ?