A reasonably quick to build facsimile [of full size model] can be made out of foam and skinned with tape for durability. Use coke can tabs taped to the control surfaces for "free flight" trim....then later add servo controlled surfaces with tape hinges and a basic [cheap] motor. Just do it down and dirty to get the hand launchand low powered flight ironed out before you commit to crafting the finished, labor intensive product.
I'd build a full size foam mock up with a flat bottom and airfoiled top...just to simplify it and to quickly ensure that it comes out.
with no warps.
Heavy grit belt sander rolls mounted on hunks of 2x4 lumber make great tools for hogging out the foam. Have a shop vac rigged to capture the mess as you cheese grate it off. I think within 2 hours you could whip out something like this from 1 inch thick high density foam. 3M77 makes quick glue joints, just spray a light coat on both surfaces. Once you sort out the crude prototype well enough to fly with limited power then you should be able to confidently tackle the high speed model.