Regardless of how good the shop is, and how experienced the welder is, IF by some strange reason the welds come apart, or IF a piece chips for any reason, what do you think that will do once the pressure boosts the metal pieces down into your engine. A big chunk probably won't make it past the intake valve, but it definitely reap havoc once it gets stuck. A smaller piece will get by tho, and the things it will do to your cylinder walls, heads, pistons, etc... will make you shudder.
Thus the WHOLE plate idea came to him and a few others (seen it before) because if something comes undone, worse case is it blocks the air way and the engine starves itself and dies. Not destroys itself from the inside causing a need for a whole new motor.
Not saying what you did, is ineffective, or a bad idea. But it is, considerable more dangerous too given what can happen, or should I say, what HAS happened before. But again, thanks for sharing.