It depends on design TSR and whether fixed or variable pitch. The penalty for low/no twist at TSR 4-5 is perhaps 3% in efficiency. The penalty increases at higher TSR.

Remember, the outer 25% of the blade is doing most of the work, so if the blade angle there is near correct, you will do pretty well.

One of the advantages of variable pitch is the ability to partially compensate for lack of twist. I'm talking about active pitch control, not the protection schemes. It can be set quite coarse for good start-up and then tuned for the desired TSR.

If you want twist, I would think that your fancy foam cutting machine could be programmed to give you linear twist. Progressive twist would not be possible, of course.

arctan(1/8)=7 degrees

7 deg - 6 deg = 1 degree

That would be fine for the tip, but a foot inboard, the speed ratio is different:

3 ft / 4 ft * 8 = local TSR of 6

Now the airfoil is experiencing a higher angle of attack:

arctan(1/6)=9.5 degrees

and its lift coefficient is higher (good) but its drag coefficient is also higher (bad).

The blade will do just fine up to the 2 foot station, at which point it stalls.  There is still some lift generated, but the drag is really high and that's a torque that slows things down.

arctan(1/4)=14 degrees   - getting close to stall!

The torque that slows down the prop forces it to run at a lower TSR.  Oops that throws the previous calculations out the window - and its not going in a good direction.  Slowing down the blade means that stall begins even farther out.  You could lose about 1/3 of the disk area at the root, which otherwise would be helpful.