Power brake conversion issue

Hi,

I trying to figure out how to increase the diameter of a brake master cylinder bore.

Story is, I did a power brake swap into a vehicle that had manual brakes and a drum/drum setup.

The replacement came from a disk/drum vehicle. I used the MS from my drum/drum brakes and added it to the booster.

Now I’m finding that there is 1/8” difference between the two and this is probably causing a vacuum leak. (The drum/drum MS is smaller)

Other observations are:
I had full pedal travel when bleeding.
Rock hard pedal with engine on, or off.
Brakes do work. I’ve tested them with all wheels raised, not driven on the street.

New setup is used and untested before install.
I was thinking that maybe I could wrap the heck out of the MS bore with teflon tape to increase its diameter and put it back on.
What do you think? Safety issues?

Thanks