I'm glad you had use of it.
I used a mod to allow me to rotate it in 1 degree increments. I think, it was called Editor Extensions.
I'd start out at 5 degrees. Time it to 450 m/s in level flight at sea level (if it'd even do that). Then go back to hangar and and make small adjustments up or down, test again to see if would shorten the time.
In my opinion, exact angles aren't really required, though, except for reproducibility, like if you have to pull the wings off for a redesign, and want to put them back on at the same angle.
I haven't actually played KSP for a while, so