How thin can I go

[pepe]

Quick question, I have limited space, about 35 inches wide by 24 inches deep, so I was thinking on making a wide barrel vault, How thin can I make the dome if I am using bricks, I thought of cuting the smaller bricks in half the long way and that would give me almost a 2 inch width. Bricks cut would be about 8Lx2Wx1.5H.

Am I chassing dragons???