John.....great vision as usual
It's hard to see from your side-on image but it seems you have three separate curves at the moment??? I would make the instrument mounting surface as one continuous curve (in top view).
Because each instrument has a flat mounting flange, and you main surface is curved.....this is a negative curve in your case, you have to raise or depress the surface locally around each shape. This will look much sweeter than having the main surface stopping and starting.
Attached is my Camaro instrument fascia which is one-piece vacuum formed ABS over a plywood/bondo male mold. You can see that each penetration has its own flat flange about 3/16" wide. The radii around the holes are much softer than you will be able to achieve in fiberglass, but I had to go that route for the vacuum form material to flow into the flat areas. Top left air outlet needed raising AND lowering the attaching flange because of the complex (compound) curve at the end of the dash.
BTW....that grill and surround are a commercial stainless steel sugar shaker like a donut store would have.....shhhh.....our secret
Also my main crash pad surface is a positive curve (with the center higher than the ends) ...... The central warning light area was then machined flat, the border trenched out, and the depressed flanges go deeper again. NEVER CREATE A FLAT SURFACE ON AN AUTO BODY because surrounding curves will make it look hollow.......also shrinkage around edges when the resin cures will pull your surface hollow. Even on a long wide panel that you want to look flat (like a fascia between tail lamps for example) should have 3/16" positive or negative curve in it......never use the plywood dead flat.
My instrument pad is loosey goosey compared to what yours can be ....cos mine is racecar and both left hand and right hand were done in TWO EIGHT HOUR DAYS! You will get better definition using gel coat and glass.