Nothing wrong with a zero deck piston. Mine are at zero deck( flattops)
I suspect that is what the build is using. Probably somewhere around a 60cc head which would yield about 12.5 compression like stated in the build.
Yes, with a 9.200 deck you are really cramming the piston with a 4 inch stroke, but it will obviously work.
There are a few( I believe Molnar is one) that offer a 3.79 crank. Obviously won’t yield as many cubes, but imo, a better way to go. Probably still going to need a custom slug, so half dozen of one, half dozen of the other.
If I am not mistaken, think I have seen the use of a 3.79 crank even with a 9 inch deck.
Longer crank in this build won’t have to run it as many rpm’s to make power. So that is plus for a bracket deal.