Tres,
Your close but would end up with a nipple where the air blows into the acrylic. If that will work for you, go for it
If you want a bettter dome....
Make 3 pcs of 3/4" material total:
On the bottom goes the solid sheet with the 1/4NPT tapped into the middle. over that hole place a 1/4" thick disc on a coupla 1/4" risers, the disc is there to diffuse airflow to the outside.
On top of the bottom piece, make another with the hole diameter equal to the desired dome diameter. Screw this piece to the bottom.
Make another just like previous piece, keep this piece free.
Put your acrylic in the oven, heat until very pliable. Place the heated acrylic on the 2-piece assembly, place the free piece on top and clamp it down using quick clamps. Blow air to the desired height is reached.
Trim flashing.
Done.
I don't like putting wood in the oven so that's why we do it this way. Your previous way will work but wood easily can warp in the oven causing a deformed dome. This way also negates the need for the large o-ring which will get destroyed by the hot acrylic.
HTH,
James