Yes, to balance a control surface, the proper weight must be added forward of the hinge line AND, to do this correctly the control surface should be removed and "jig" set up so there's little resistance with all the hinges.
An "arm" must be added with weight possibly at the tip but doesn't have to be. The farther the arm is from the hinge line, the less weight is needed for balance.
Google "balanced control surface on an aircraft."
Simple science and aerodynamics 101.
As Howard says, there is more to it than simple mass balance. The spades actually do add mass in front of the hinge in fact on some of the 4/4 airplanes we also add lead to the retaining plate for the spade itself. On my laser there was 1 1/2 pounds of lead along with the spade 2 1/4 pounds total. That was there to counter a wing flutter issue the Lasers have and Dr Tolve sorted out. Kermit Weeks recently posted a video of Tolve conducting a ground vibration test of the Gee Bee R1 of his in order to determine the flutter characteristics of he R1. He pretty much determined the cause of the original airplanes' demise.
There is some hinge moment created by the mass of the surface that much is true but it is not that much with these very light surfaces. Flutter is like a spring mass system where the spring comes from the aerodynamic force generated by the displacement of the surface. Of course in the case of being around the hinge it becomes the rotational version and it's torque versus moment of inertia. When the center of mass is at the hinge, the opportunity for flutter is eliminated. This same spring force which is caused by the surface displacement is what the spades offset. End of the day, mass balancing will not create the same hinge moment reduction as do the spades.
If you wish, you could compare the spade with a horn balance which is most often located at the end of the wing. Another way is to offset the hinge further back in to the surface which will be the approach of the new airplane. Some airplanes like the Cessna Citations use both a balance horn and offset hinge. If you are interested, I can provide tons of good literature on the subject. Bottom line is mass balancing is for flutter prevention while balance horns and spades are for moment reduction aka control stick force reduction.
I have not measured the force at the handle. Perhaps a creative EE would step in and help but I can provide a qualitative analysis. Unfortunately I have not been able to convince any of my local other pilots to fly the A-B test on my airplane despite my most insistent efforts. So my estimate is that the no spade installation is at something like 5 pounds differential up to down. I have no clue what it really is, maybe it's 2 but for discussion use I'll say 5 pounds. Adding just the strut with the retaining plate which has about 1 square inch surface area changes that a bit noticeably to about 4 - 4 1/4 pounds differential. Adding the spades brings that down to around 2 - 2.5 pounds differential. I am planning on taking the total area of the plates up to 20 (10 each) square inches and hope that they remain linear. If not the impact is that I go back to the initial or intermediate state. Here's one point of caution I have to remind myself of is that elevator is a contributor also and I will not shoot for the zero moment point and solely the plateau zone where the hinge moment of the flap nears zero.
I realize that your objection has nothing to do with the flying or handling qualities and everything to do with the aesthetics. Personally, I don't care what it looks like as long as it works well.. I am a performance oriented individual and I'm not a lemming. I am both scientist and engineer, therefore I am always in a research and development mode. I make these inputs, even if they aren't received well as I think they are interesting. From the PMs I get, I won't stop. The airplane these are flying on will continue to have the spades installed for it's foreseeable future. They are that good of a change and I'm going tell you I have tried dozens of the you gotta try this'... Most are "meh". There's simple way to prove me wrong, put some on your airplane and try it. I'll even help you.