I have always been interested in making a model like that, but it has always been tough to validate numerically. Since you are trying for VTOL, there is no pressure on the lower surface (at a normal high angle of attack the pressure on the bottom is much higher than atmospheric) which means in order to get a similar pressure differential, the required velocity on the upper surface is almost doubled. The Custer wing was only slightly improved over a conventional wing design (the weight of the complex spar ended up almost making the blown section negligible) so it seems like in order to get enough of a Cl to do a vertical takeoff, the air velocity is going to have to be extremely high. It seems like it would work though...blowing across the top of a piece of paper is essentially doing the same thing.<div>
</div><div>And in defense of Coanda devices, there have been numerous successful prototypes, along with hundreds of well-performed studies. There is an entire AIAA book called "Applications of Circulation Control Technologies" that has numerous papers on the subject...and I have personally seen a model obtain a measured Cl of between 5 and 7 on a sting balance (without my hand in the freestream). And they are designed for slow speed, high lift; so comparing them to helicopters is not fair at all.</div>